MXPA05005042A - Method of obtaining rubber pellets from used tires - Google Patents

Abstract

The invention relates to a method of obtaining rubber pellets from used tires. The inventive method comprises a series of steps which take account of the structure of the tire, including the following steps consisting in:collecting used tires that are equipped with a tread and lateral faces, in which the tread includes an inner layer and an outer layer and each lateral face includes a flange along the inner edge thereof;separating the tread from the lateral faces;culling the tread transversely through the inner layer and the outer layer in order to form a tread strip culling the tread strip thus obtained in order to form pellets from same;detaching the flange from the separated lateral faces;and cutting the flange-less lateral faces in order to form pellets therefrom.

Description

"PROCEDURE FOR THE OBTAINING OF RUBBER NODULES FROM DISPOSAL TIRES" FIELD OF THE INVENTION The present invention refers to the technique for separating and cutting the different elements that constitute a tire, and more particularly, it is related to a process for obtaining rubber nodules from waste tires.

BACKGROUND OF THE INVOLVEMENT At present, due to the constant growth of the vehicle fleet, the tire waste has been increasing year after year, it is estimated that in Mexico 25 million tires are discarded annually and in the U.S. approximately one tire per inhabitant, which is one of the most serious pollution problems of recent times, even more so if one takes into account that there is great complexity to store, destroy or find a practical use to the large volumes of waste tires. One of the main reasons for this problem is due to the physicochemical properties that tires acquire when subjected to vulcanization, so that their elimination, recycling or transformation is extremely complicated. In Mexico, used tires usually end up in streets, vacant lots, open dumps and in few cases in landfills. For this reason, these deposits quickly become a health problem, since they develop pests such as rats and mosquitoes. Recently, the Cement Industry has used waste tires as fuel for its kilns, since the tires are mainly formed of hydrocarbons and contain a calorific value that is very similar to that of fossil fuels used in this industry, and even higher than that of the carbon. The tires are incinerated at temperatures of the order of 1450 ° C, which according to this industry, ensures a complete combustion and without residues such as soot and other pollutants. However, currently only a limited number of tires are allowed for this purpose. Another application of waste tires has been as filling material for road and bridge slopes, but due to its physical and chemical characteristics, its use is very limited. With respect to the recycling of tires, there are technologies in which the main materials are recovered with which a tire is manufactured, that is, rubber, fibers and polymer and steel ropes. These recovered materials are mainly used to make new tires, manufacture rugs, waterproofing, molten steel, cork and rubber agglomerates, shoe soles, etc. inclusive, old tires are re-vulcanized with new rubber. In the recycling of tires, they are divided, cut or pulverized to obtain particles, strips, plates or nodules that can be incorporated in the products and processes mentioned above. However, recycling is certainly complicated since, due to the particular structure of a tire within which there are polymer and steel cords between the rubber layers, obtaining particles with a homogeneous structure is not a simple task nor direct To explain more clearly the above, it is convenient to indicate that a tire has a structure in which two main parts are defined: the tread that makes contact with the pavement and the side faces that allow the tire to be mounted to a rim. In relation to the above, the tread is in turn constituted by an inner layer and an outer layer or tire floor, which is properly the part that makes contact with the surface of the pavement. The inner layer is mainly integrated by a casing or frame inside which there is a layer of sealing rubber, layers of polymer fiber cords covered with rubber and depending on the type of tire, stabilizing belts. For its part, the external layer or floor of the tire is composed essentially of rubber and there are provided bars, grooves, grooves and shoulders, which form the tire pattern. Describing a little more the conformation of the inner layer, it can be mentioned that the shell or frame is composed in its inner part by the sealing rubber layer, whose function is the retention of air because it is impermeable to it. On the sealing rubber layer, the layers of strings of polymeric materials such as rayon, polyester, nylon or steel are covered with rubber to prevent friction thereof. Finally, in the outermost part of the carcass and on the layers of polymeric or metallic cords, there are optionally the stabilizing belts whose main function is to provide stability and uniformity to the tread when the tire is rotating at high speeds, which contributes to the resistance, less wear, traction and handling of the tire. The material commonly used in stabilizing belts is steel, as it provides strength and stability to the tread without adding much weight to the tire. Now, in relation to the second of the main parts that form the tread, that is, the outer layer or floor of the tire, it can be mentioned that the grooves provided in said external layer are designed to drain water, waste, cool the tire, generate traction and prevent lateral slippage of the vehicle. In addition, the slots are designed to eliminate the emission of noise caused by air channeling. On the other hand, the grooves included on the floor of the tire have the function of increasing the cooling or cooling of the tire and contributing to its pulling capacity. While the shoulders join the tread with the side faces; the shoulders are designed taking into account the bending of the lateral faces, resulting in a perfect assent of the tread on the pavement. In addition, the shoulders help weight transfers on the tire, when a vehicle goes through curves. On the other hand, as mentioned above, the second basic structure of a tire are the side faces, each of which includes an eyebrow that forms the inner ring thereof. The lateral faces of the tire are joined to the tread by the shoulders and are formed by rubber compounds with a high resistance to fatigue by bending, additionally they can present within the same steel cords that provide greater resistance. For its part, the eyebrow is formed by steel wires in the form of rings. The wires are copper coated to prevent oxidation and, in addition, are individually insulated by rubber compounds to prevent friction. The function of the eyebrow is to anchor the tire in the rim and it must have a high resistance to rupture, in such a way that the eyebrow is filled with a hard rubber compound to withstand the rigors of the tire assembly. During the manufacture of a tire, the eyebrows are joined to the side faces in the assembly of the tire, and subsequently, they are completely joined by the vulcanizing process. Once having explained the basic structure of a tire, it is important to mention that in the prior art, there are machines that allow separating the two main parts that make up a tire, such is the case of Mexican Patent No. 188,444 belonging to the same inventor as et of the procedure that is described in this document. Said patent relates to a tire cutting machine, by means of which it is possible to efficiently separate the side faces of the tread in order to reduce the volume occupied by the waste tires. However, it is not mentioned how the separated parts must be processed to obtain homogeneous particles or nodules that can be recycled in the aforementioned processes and products. Also, in the prior art, Mexican Patent No. 160,377, which describes a machine that has the purpose of cutting waste tires, is present, said machine employs a structure having a cylindrical anvil roller, mounted rotatably therein. In addition, the machine employs a pair of blade rollers in the structure, which rotate on axes parallel to the axis of rotation of the anvil roller, said blade rollers angularly spaced apart from each other, relative to the axis of the anvil roller, so that the tires pass through the anvil roller between the rollers with blades, and in which almost rectangular diamond shaped tire cuts are obtained. However, this machine like other existing ones does not take into account the structure of the tire, since in the machine, the tires are fed in a whole way and the result is a high consumption of energy, in addition to the rubber rhombuses obtained not They are uniform, in such a way that ropes and fibers protrude from the diamonds, which can hurt the personnel who work with them. Another case is present in the Mexican patent 160,376 which describes a machine similar to that of the patent 160,377 this machine comprises an anvil roller and a roller with blades that rotates around the axis parallel to the rotary axis of the anvil roller. In a similar way, this machine cuts the tires in pieces without differentiating or obtaining the maximum benefit from the different parts that make up the tires. Another prior art document that is important to mention, is the Mexican patent application 9401943, which describes a machine consisting of a pair of platforms where the tire is placed where the rubber is cut through the tire cutting operations. high pressure fluids, however, the disadvantage with this type of machines is the great cost of operating a fluid under high pressure, also has the disadvantage of carrying out processes to clean and recirculate the fluid used in the operation of the machine. As can be seen, the prior techniques are limited to randomly cutting the waste tire, or, by very expensive machines and do not provide a logical sequence to obtain the maximum benefit of the constituents of the tire, in addition, said techniques do not distinction in the particular way in which rubber, polymer and metal strings are related in a tire.

BRIEF DESCRIPTION OF THE INVENTION As a consequence of the foregoing, it has been sought to eliminate the drawbacks of the techniques and procedures for the recycling of scrap tires from the prior art and to provide a procedure for obtaining rubber nodules from waste tires, wherein said procedure can be carried out mainly through simple and organized operations, obtaining rubber nodes that are homogeneous so that they can be more easily handled in a wide variety of recycling applications. In particular, the process for obtaining rubber pellets from waste tires of the present invention, comprises the following steps: a) collecting waste tires having a tread and side faces, wherein the tread band bearing includes an inner layer and an outer layer; and each tateral face includes an eyebrow at the inner edge thereof; b) separate the tread from the side faces; c) transversely cutting the tread through the inner layer and the outer layer to form a strip of the tread; d) cutting the strip of the tread obtained in the previous step to form nodules therefrom; e) detaching the eyebrow from the side faces that were separated in step (b); and, f) cutting the side faces without eyebrows obtained in the previous step to form nodules therefrom; With the arrangement and sequence of the previous stages, rubber nodules are obtained from the tread and from the lateral faces. An advantage of the method is that the nodules obtained from the two main parts of the tire have a regular size and shape, furthermore, said rubber nodes include polymeric and metallic fibers or ropes that do not protrude from them, so that the subsequent handling of the nodules do not represent risks for the personnel who work with them. In a first preferred embodiment of the method of the present invention, step (d) or "first stage of nodular cutting", is performed in two steps, in the first of them, longitudinal and parallel cuts are made to each other on the strip of the tread, thereby forming a first plurality of more strips, and in the second step, transverse cuts are made and parallel to each other on said thin strips to form the rubber nodes. The process of processing the tread in this sequential and organized way, represents as an advantage the adequate control in the size of the rubber nodules formed and, above all, it prevents the fibers and ropes present in the tread protruding from the nodules. of rubber formed. In a second preferred embodiment, the method of the present invention comprises a further step after separating the tread from the lateral faces in the separation step (b), the additional step consists in separating the outer layer from the inner layer of the tread, these layers are subsequently cut transversely to form a strip of the outer layer and a strip of the inner layer, which are then cut independently in the first stage of nodular cutting (d) to form rubber nodes from each of said strips. This modality has the advantage of obtaining nodules essentially formed by rubber coming from the outer layer of the tread. In a third preferred embodiment, the method comprises a step of screening the nodules obtained from the tread and from the lateral faces in the first stage of nodular cutting (b) and in the second stage of nodular cutting (f). The purpose of the sieving is to separate and classify the nodules according to their size, since some of the nodules can differ in size and shape, especially those that are formed from the lateral faces in the second stage of nodular cutting. (f) because the side faces have circular edges by their very nature. As you can appreciateIt is an object of the present invention to provide a method for obtaining rubber nuggets from waste tires, wherein the main parts of the tire are cut and separated in a systematic manner, facilitating the recycling of the tires. Another object of the invention is to provide a process for obtaining rubber nodules from waste tires, in which nodes essentially composed of rubber and rubber nodes can be obtained with fibers or ropes therein. It is still an object of the present invention to provide a method for obtaining nodules from scrap tires, where the sequence of stages represents in practice a lower energy use and consumption than feeding the whole tires to the machines of the art. previous.

BRIEF DESCRIPTION OF THE FIGURES The novel aspects that are considered characteristic of the present invention are set forth with particularity in the appended claims. However, the operation, together with other objects and advantages thereof, will be better understood in the following detailed description of certain specific embodiments, when read in relation to the accompanying drawings, in which: Figure 1 is a perspective view of a portion of a transversely cut tire. Figure 2 is a flow diagram of the process for obtaining rubber pellets from waste tires of the present invention. Figure 3 is a flow chart of the process for obtaining rubber pellets from waste tires, in accordance with a first specific embodiment of the present invention. Figure 4 is a flow chart of the process for obtaining rubber pellets from waste tires, in accordance with a second specific embodiment of the present invention. Figure 5 is a flowchart of the process for obtaining rubber nuggets from waste tires, in accordance with a third specific embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION In order to explain the advantages and the organization of the method of the present invention, it is convenient to describe the general structure of a tire, for which initial reference is made to Figure 1, in which it is shown a tire 10 which is constituted by a tread 20 that makes contact with the pavement and side faces 30 to mount the tire 10 to a wheel. In this same figure, it is observed that the tread 20 comprises in turn an inner layer 21 and an outer layer 22. Within the first of these layers also known as frame or shell, there is a layer of sealing rubber 23 and over There are various layers 24 of polymer fibers or rubber-coated metal cords in the rubber 10, in the tire 10 shown in FIG. 1, stabilizing belts 25 are additionally observed. As regards the outer layer 22, it has a running floor 26 and shoulders 27 for connecting the tread 20 with the lateral faces 30. In this particular, it is appreciated that the inner edge of the lateral faces 30 is formed by an eyebrow 31 that allows the tire 10 to support the operations of assembling and disassembling the tire. tire 10 to a rín. Having described the general conformation of a tire, particular reference is made to Figure 2, which shows a flowchart of the essential steps comprised by the method 100 of the present invention, which starts with the storing stage 110, where waste tires 10 are gathered, likewise, in this storing stage 110, the waste tires 10 are preferably classified according to their physical state, type and size. Subsequently, in the procedure 100, the separation step 120 is carried out, in which of each collected waste tire 10, the tread 20 is separated from the side faces 30. Once having separated the two main parts of the tire from scrap 10 in the separation step 120, the tread 20 is sent to the cross-sectional step 130, wherein said tread 20 is cut transversely through its outer and inner layer so as to form a strip 28 of the tread. Then, the first stage of nodular cut 140 takes place, where the strip 28 of the tread is cut in such a manner that nodules of rubber 11 are formed therefrom. Now bren, the procedure 100 also contemplates forming nodules from the side faces 30 that were separated in the separation step 120, for which said side faces 30 are processed in the peel-off step 150., wherein the eyebrow 31 of each side face 30 is removed and discarded. After the stripping stage 150, the side faces 30 without eyebrows are received in a second nodular cutting stage 160, where said side faces 30 are cut in such a way that other rubber nodes 11 are formed. In relation to the above, the main reason why the eyebrow 31 is detached from each lateral face in the detachment stage 150, is because the eyebrow has a complex structure and very different from the rest of the lateral face 30. In the eyebrows, wires are found of steel coated with copper and rubber, which would complicate the realization of the second stage of nodular cutting 160 and would form nodules of rubber 11 with two very different structures. On the other hand, the rubber nodules 11 coming from the strip of the tread 28 and from the side faces 30 without an eyebrow, share a much more similar structure among them, that is to say, they include fibers and cords in their interior, such as mentioned, the side faces 30 have steel cords as the tread band, so that the nodes 11 can be mixed to be taken to the respective facilities where they will be recited. In the process of the present invention, the rubber nodes 11 obtained in the first and second nodular cutting stages 140 and 160, respectively, have a preferred size of about 6.4 mm to about 50.8 mm. They also have a quadrangular or rhomboidal shape. As can be understood from what is described for FIG. 2, in the separation stage 120, the cross-sectional stage 130, the first nodular cutting stage 140, the detachment stage 150 and the second stage of nodular cutting 160, mainly cutting and separation operations are carried out, in such a way that said steps are carried out using manual cutting tools or cutting machines operated mechanically, hydraulically or electrically. For example, the manual cutting tools that can be used are scissors, guillotines, knives and knives. While the cutting machines can be shears or presses with blades and multiple cutting discs. And more specifically, the separation step 120 can be performed using the machine described in Mexican Patent No. 188,444. One aspect that is important to mention is that, in the second stage of nodular cutting 160, longitudinal and transverse cuts are made at the same time in the manner of a grid on the side faces 30 in order to form the rubber nodes 11. Of course, that some of the rubber nodes 11 will have a circular or rounded shape due to the circular contour of the lateral faces 30, however, this situation will be addressed a few paragraphs later. The present invention can be carried out according to specific modalities, the first of which is shown in Figure 3, the method of this modality identified with reference 101, comprises all the steps that those described for Figure 1, ie, comprises the storing stage 110 of waste tires 10; the separation step 120, where the side faces 30 are separated from the tread 20; the cross-sectional step 130 of the tread 20; the detachment step 150 of the eyebrow 31; and, the first and second stage of nodular cutting 140 and 160, where the strip 28 of the tread and the side faces 30 are cut in the form of rubber nodes 11. However, in this first preferred embodiment, the first Nodular cutting stage 140 is carried out in two steps, in the first step 141, longitudinal and parallel cuts are made on the strip 28 of the tread entering this first stage of nodular cutting 140, in such a way that a first plurality of thinner strips 29 are formed, and in the second step 142, transversal and parallel cuts are made to each other on said thin strips 29 in order to form rubber nodes 11. Processing the tread strip 28 in this sequential and organized way, it represents as an advantage to have a precise control in the size of the formed rubber nodes 11, as well as to avoid that the cords and fibers that are present in the tread protrude n of the rubber nodules 11 formed.

Preferably, the first and second pass 141 and 142 are executed by cutting machines having a plurality of blades, blades or cutting discs spaced parallel to one another. In an alternative embodiment of the method, in the first nodular cutting stage 140, transversal cuts are made initially parallel to each other on the tread strip to form a second plurality of strips of the same width as that of the tread, and subsequently, parallel cuts are made to form rubber nodes of this second plurality of strips. This method also allows control over the formed nodes, however, due to handling issues of the tread strip 28, it is preferable to initially make the parallel cuts along said strip 28 as outlined in the figure 3. Referring now to Figure 4, there is shown a second specific embodiment of the method of the present invention, the second embodiment, identified as 102 comprises, as can be seen the storing stage 110 of waste tires 10; the separation step 120, where the side faces 30 are separated from the tread 20; the cross-sectional step 130 of the tread 20; the detachment stage 150 of the eyebrow 31; and, the second nodular cutting stage 160 where the side faces 30 without eyebrow are cut in the form of nodes 11. However, in the procedure 102 of this second embodiment, after the separation step 120, the tread 20 is subjected to a division step 170, in which the inner layer 21 of the tread 20 is separated from the outer layer 22. Subsequently, said bands 21 and 22 are cut transversely and separately in the cross-sectional stage 130, to obtain a strip of the inner layer 131 and a strip of the outer layer 132, then these strips 131 and 132 are cut independently in the first stage of nodular cutting 140 obtaining rubber nodes 11 and 1T, of which the nodules of rubber 11 incorporate ropes and fibers therein, while the rubber nodes 11 'consist essentially of rubber. Finally, reference is made to Figure 5, which shows a third specific embodiment of the method of the present invention, this third embodiment identified as 103, once again includes the storing stage 110 of waste tires 10; the separation step 120, wherein the side faces 30 are separated from the tread 20; the cross-sectional step 130 of the tread 20; the detachment step 150 of the eyebrow 31; and, the first and second stage of nodular cut 140 and 160, where the tread strip 28 and the side faces 30 are cut in the form of nodes 11. However, taking into consideration that the side faces 30 have a circular shape and that in many waste tires the band of bearing 20 has a wear that is not uniform on its surface, the procedure 103 of this third embodiment comprises the performance of a screening stage 180, in which the rubber nodules 11 coming from the first and second stages of nodular cutting 140 and 160 are passed through screens, screens or screens to separate those nodules that do not have the preferred size of about 6.4 mm to about 50.8 mm. Although specific embodiments of the present invention have been shown and described in the foregoing description, it should be emphasized that numerous modifications are possible, for example, the direction of the cut in the tread can be varied to obtain nodules of different shape. Therefore, the present invention should not be restricted by what is established in the state of the art and by the appended claims.

Claims (14)

1. NOVELTY OF THE INVENTION CLAIMS 1.- A procedure for obtaining rubber pellets from waste tires, characterized in that it comprises the steps of: a) collecting waste tires having a tread and side faces, wherein the tread includes an inner layer and an outer layer; and each side face includes an eyebrow at the inner edge thereof; b) separate the tread from the side faces; c) transversely cutting the tread through the inner layer and the outer layer to form a tread strip; d) cutting the strip of the tread obtained in the previous step to form nodules therefrom; e) detaching the eyebrow from the side faces that were separated in step (b); and, f) cutting the side faces without eyebrows obtained in the previous step to form nodules therefrom; whereby, rubber nodules are obtained from the tread and the lateral faces, the nodules having a size and form regular, and include in their interior fibers and polymeric and metallic ropes that do not protrude from them.
2. 2. A process for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that in the storing stage (a) the waste tires are classified according to their physical condition, type and size
3. 3. A process for obtaining rubber nodules from waste tires, according to claim 1, further characterized in that the separation step (b), the cross section (c), the first stage of Nodular cutting (d), the detachment stage (e) and the second stage of nodular cutting (f) are carried out using manual cutting tools or mechanically, hydraulically or electrically driven cutting machines.
4. 4. A process for obtaining rubber nodules from waste tires, according to claim 3, further characterized by manual cutting tools are scissors, guillotines, blades and knives.
5. 5. A process for obtaining rubber pellets from waste tires, according to claim 3, further characterized by cutting machines are shears or presses with blades and multiple cutting discs. 6. A process for obtaining rubber nodules from waste tires, according to claim 1, further characterized in that the rubber nodules obtained have a size of
6. 6.54 mm to 50.8 mm.
7. 7. A process for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that the rubber pellets have a quadrangular or rhomboidal shape.
8. 8. A process for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that the first stage of nodular cutting (b) of the strip of the tread is performed in two steps, in the first of them, longitudinal cuts are made and parallel to each other on the strip of the tread, thus forming a first plurality of thinner strips, and in the second step, other transversal and parallel cuts are made between Yes on said thin strips to form the rubber nodules.
9. 9. A process for obtaining rubber pellets from waste tires, according to claim 8, further characterized in that the first and second step are executed by cutting machines that have a plurality of blades, blades or discs of cutting separated in parallel with each other.
10. 10. - A procedure for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that in the second stage of nodular cutting (f)At the same time, longitudinal and transverse cuts are made in the manner of a grid on the lateral faces in order to form the rubber nodules.
11. 11. A process for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that it further comprises the step of: g) separating the outer layer from the inner layer of the tread , these layers are subsequently cut transversely in the cross-sectional stage (d) to form a strip of the outer layer and a strip of the inner layer, which are then cut independently in the first stage of nodular cutting (d) for forming rubber nodules from each of said strips.
12. 12. A process for obtaining rubber nodules from waste tires, according to claim 11, further characterized in that the nodules obtained from the strip of the outer face of the tread essentially consist of rubber .
13. 13. A process for obtaining rubber pellets from waste tires, according to claim 1, further characterized in that it further comprises the step of: i) sieving the nodules obtained from the tread and from the faces laterals in the first stage of nodular cutting (d) and in the second stage of nodular cutting (f).
14. 14. A process for obtaining rubber pellets from waste tires, according to claim 13, further characterized in that the sieving stage is performed by means of screens, screens or screens.