Method for recycling elastomers, recycled elastomers, and uses of recycled elastomers

Abstract

The present invention relates to a method for recycling solid waste from vulcanized elastomers, either sulfur-based or crosslinked with peroxides. In this context, the invention proposes to recycle said waste by radical decrosslinking in the presence of ozone and a decrosslinking agent, without the use of high temperatures. The invention also relates to the recycled elastomers obtained by said method and to the use of said recycled elastomers.

Description

[Technical field]

[0001] The present invention relates to a process for recycling solid waste of sulfur-based or peroxide-crosslinked vulcanized elastomers, and to the recycled elastomers obtained by said process.

[0002] The present invention also relates to the use of recycled elastomers. [Background technology]

[0003] Due to their inherent properties related to crosslinking, elastomers generate waste after production and consumption, causing serious environmental problems related to the disposal of vulcanized rubber, which is usually incinerated. In this context, rubber recycling consists of converting elastomers into processable materials that are compatible with virgin rubber.

[0004] The most efficient method for recycling rubber is to break the crosslinks by thermal, chemical or mechanical means while leaving the main chain structure intact. In this context, many methods known in the art, such as heat, present problems related to the high temperatures used to break the crosslinks of the recycled elastomeric material, which means high energy consumption and degradation of the reclaimed material, as well as undesirable secondary reactions. Moreover, in the context of mechanical methods for recycling rubber, the high shear rates typically used usually lead to random crosslink breaks, producing recycled products that cannot be crosslinked again with virgin rubber.

[0005] Chemical recycling, on the other hand, selectively breaks the crosslinks and reduces the glass transition temperature (Tg), making the polymer chains more mobile and allowing them to be incorporated into virgin elastomers. Depending on the efficiency of the vulcanization and / or crosslinking reactions carried out to obtain the virgin elastomer, chemical recycling methods can be more or less complicated, depending on the energy of the crosslinks involved.

[0006] Vulcanization systems can be classified, for example, by their sulfur and accelerator content, and are considered efficient when the sulfur content is between 0.3 and 1.0 parts per 100 parts of rubber (PCR) and the accelerator content is between 2.0 and 6.0 parts per 100 parts of rubber (PCR). Efficient systems induce the formation of monosulfide bonds (CSC) and disulfide bonds (CSSC), which increase the thermal and oxidative stability of the material due to the presence of sulfur bonds with the polymer, but this is also associated with the inability to exchange, rearrange, or cleave, and therefore to relax mechanical tensions without breaking the main chain. In this context, decrosslinking reactions require more energy. It is therefore common to use thermal and / or mechanical chemical recycling methods that use chemical reagents with high temperatures and shear, which not only cause problems related to the material degradation and secondary reactions mentioned above, but also increase costs due to high energy demands and long durations. In this context, it is important to note that the maintenance of the desired mechanical properties and the costs associated with recycled elastomers are related to the recycling method. Furthermore, the processes known in this connection generally involve the use of large amounts of organic solvents as well as compatibilizers.

[0007] In the peroxide crosslinking method, organic peroxides are used to crosslink rubbers that are saturated or do not contain reactive groups capable of forming crosslinks. Peroxides as crosslinking agents do not penetrate into polymer chains but generate radicals that form C-C bonds between adjacent chains in the polymer matrix. Peroxide crosslinking gained importance with the development of saturated synthetic rubbers such as EPM, EPDM, and EVA. The bond energy of C-C bonds is even higher than that of S-S and C-S bonds, so currently existing recycling alternatives either have limitations as explained above or are only efficient at decrosslinking sulfur-based bonds and not at breaking peroxide-based crosslinks.

[0008] The current state of the art includes literature that envisages recycling polymer waste, including elastomer waste, using ozone and other decrosslinking agents.

[0009] The document US 5,373,067 refers to a method for recycling polymeric materials based on ethylene vinyl acetate (EVA). Furthermore, this document proposes the use of recycled materials as raw materials in conjunction with virgin EVA. The essential objective of US 5,373,067 is to convert EVA residues without completely destroying the polymer, i.e. limiting the cleavage of specific bonds to a controlled cleavage of the molecules, without cleaving functional groups. To this end, the method of US 5,373,067 involves particulating the polymeric material (i.e. involving mechanical methods), incorporating the obtained polymeric particulates in an organic solvent suitable for diffusion within the polymer network of the material and for the expansion of said network, and exposing the reaction medium to an ozone current as a decrosslinking agent, resulting in the depolymerization of the initial material and the formation of active sites. With regard to the use of recycled elastomers as raw materials in relation to virgin elastomers, this document shows the feasibility of using only 20% recycled material to obtain a product with identical mechanical and rheological properties to virgin EVA.

[0010] The paper by Prestes, SMD entitled "Reuse of crosslinked EVA waste through chemical recycling" also deals with the depolymerization of EVA waste. More specifically, this document deals with the recycling of EVA waste from the footwear sector for later reinsertion into the original segments themselves. In this context, this document proposes the use of depolymerized EVA waste together with virgin PVC. Prestes, SMD discloses different methods of chemical recycling, including decrosslinking with hydrogen peroxide and decrosslinking with ozone. The recycling method with ozone showed the most satisfactory results and was carried out in a reaction medium containing 1,2,4 trichlorobenzene to swell the polymeric material.

[0011] Document CN109749757 discloses a rubber / plastic waste recycling product and its preparation method, which also takes into account the technical problems of thermal degradation of rubber polymer materials and the formation of impurities associated with the heat carrier.In this regard, CN109749757 proposes a method for preparing a rubber / plastic waste recycling product, which includes a combination of recycling waste rubber / plastic by pyrolysis and recycling waste rubber / plastic by non-pyrolysis.In this regard, it teaches the integration of conversion energy from a thermal method into a non-pyrolysis method.

[0012] The paper by Rooj et al. entitled "New Route for Devulcanization of Natural Rubber and the Properties of Devulcanized Rubber" refers to the devulcanization of natural rubber using benzoyl peroxide as a devulcanizing agent. In this connection, Rooj et al. teach a chemical method and a mechanochemical method. In the chemical method, devulcanization is carried out in xylene at a temperature of about 80 °C. Furthermore, the document suggests re-vulcanizing the rubber and using it in a mixture with virgin rubber in various proportions.

[0013] The paper by Colom et al. entitled "Assessment of the devulcanization process of EPDM waste from roofing systems by combined thermomechanical / microwave procedures" refers to the treatment of ethylene-propylene-diene rubber (EPDM) waste by combining thermomechanical and microwave devulcanization methods. In this context, Colom et al. also mention benzoyl peroxide as a decrosslinking agent with high processing temperatures.

[0014] Thus, the state of the art still lacks an elastomer recycling method that does not require high temperatures, specialized equipment and the use of compatibilizers, and that covers a wide variety of elastomers, regardless of their original vulcanization / crosslinking method, thus allowing the use of large amounts of recycled material in the manufacture of articles, and even the use of 100% recycled elastomers, depending on the article being formulated.

[0015] As will be explained in more detail below, the present invention aims to solve the above-mentioned problems of the state of the art in a practical and efficient manner. Summary of the Invention

[0016] The present invention relates to a method for recycling solid elastomer waste without the use of high temperatures, specialized equipment and compatibilizers. More specifically, the present invention envisages a method comprising radical decrosslinking carried out in a solvent medium in the presence of ozone and a decrosslinking agent, and the recycled elastomers thus obtained.

[0017] The present invention also relates to the recycled elastomers obtainable by the aforementioned process, and to their use in the manufacture of articles containing them.

[0018] The object of the present invention is to provide a process route for the chemical recycling of elastomers without decomposing the polymeric material. It is therefore also an object of the present invention to obtain recycled elastomers that can largely replace virgin elastomers in the composition of new articles based on vulcanized rubber. In this context, the present invention envisages the use of large amounts of recycled elastomers obtained by the proposed method or even the manufacture of articles exclusively from recycled elastomers.

[0019] The above objects and other advantages of the present invention will become apparent from the following description. [Brief description of the drawings]

[0020] [Figure 1] 1 shows the pathway of radical formation by benzoyl peroxide in the presence of ozone. [Diagram 2] 1 shows the radical formation pathway by persulfate in the presence of ozone. [Diagram 3] 1 shows the pathway of radical formation by styrene in the presence of ozone. [Figure 4] Test specimens made from virgin SBR and a blend of 30% virgin SBR and 70% recycled SBR by weight are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention relates to the chemical recycling of solid elastomer waste, carried out in a solvent medium at room temperature in the presence of ozone and a decrosslinking agent.

[0022] More specifically, and different from the existing state of the art, the present invention uses a combination of a decrosslinker and ozone as an initiator for the formation of free radicals in said decrosslinker. These radicals attack the crosslinks of the polymer matrix and promote their decrosslinking. In this context, ozone acts simultaneously with the decrosslinking process of the elastomer.

[0023] According to the present invention, the decrosslinking agent comprises a peroxide, a persulfate, or a mixture of these or the like, or alternatively a "reactive solvent."

[0024] Peroxides, for example, have a half-life (the time required for half of the mass to decompose at the operating temperature). In conventional methods of the art based on the formation of radicals in peroxides at high temperatures, the concentration of radicals formed decreases due to thermal decomposition of the peroxide. In this scenario, the formation of radicals in the presence of ozone becomes more efficient, since it prevents the concentration of radicals from decreasing over the half-life of the peroxide. In the case of persulfates, which generate highly reactive free radicals, are more susceptible to further decomposition at high temperatures (indeed, decomposition occurs at a temperature of about 40° C.). The combined use of peroxides and / or persulfates as decrosslinking agents, or alternatively "reactive solvents", and ozone as initiator allows the formation of free radicals that attack the crosslinks of the polymer matrix. In this context, ozone, in addition to acting simultaneously in a decrosslinking method, allows the radical formation to take place without the use of high temperatures, making the radical formation even more efficient without the decomposition of the decrosslinking agent and the polymeric material. Figures 1 and 2 show the proposed pathways for radical formation by benzoyl peroxide and persulfates, respectively, in the presence of ozone.

[0025] In the case of both peroxides and persulfates, it is necessary to use a solvent as a vehicle to facilitate the impregnation of these agents into the polymer matrix of the elastomer and then the reaction with ozone and the resulting attack of the crosslinks. According to the present invention, the solvent is selected according to its solubility parameters suitable for swelling the elastomer to be decrosslinked.

[0026] Preferably, the solvent is selected from halogenated or aromatic organic solvents or mixtures thereof or the like, most preferably toluene or xylene.

[0027] For polymers with covalently cross-linked chains, such as elastomers, the polymer matrix swells due to the compatibility of the solvent system. In this way, the solvent fluid can intercalate between the elastomer chains without breaking the cross-links. The solubility of a polymer in a solvent depends on the similarity or chemical affinity between the polymers. Said affinity is defined by the solubility parameter, which is used to predict the solubility of a polymer. In order to dissolve, or simply swell, a polymer, the interactions between the segments of the polymer chain and the solvent must be greater than the solvent-solvent and polymer-polymer interactions.

[0028] A polymer with a high solubility parameter (δ) requires a large amount of energy to separate its molecules. If a second compound with a lower δ value is added to the first compound, the energy is not sufficient to separate the molecule with the higher δ value, resulting in immiscibility (BARTON, 1983). Since the solubility parameter is related to the minimum internal energy required to separate the molecules, it is possible to establish a relationship between different solubility parameters and the formation of solutions of different molecules. According to Hildebrand, in the case of a solution, the heat of mixing of the solvent and solute is proportional to the square of the difference in solubility parameters and is given by the following formula (CHARLES E. CARRAHER, 2003): ΔH m =V s V p (δ s -δ p ) 2 where Vs and Vp are the partial volumes of the solvent and polymer, defined as the mole fraction multiplied by the total volume.

[0029] Charles M. Hansen developed a correction of the Hildebrand parameters in 1966 to evaluate the effect of intermolecular interaction forces on solubilization, creating parameters for each type of interaction. For polar fluids, there are three relevant intermolecular forces to consider: - London dispersion forces (D) - exist in all non-polar molecules and even between polar molecules. London related these forces to the movement of electrons within a molecule. An instantaneous induced dipole can induce polarization in adjacent molecules, causing forces of attraction. - Permanent dipole force (P) - a measure of the polar or electrostatic side of a molecule. This distortion causes one side of the molecule to become more positive and the other side more negative, forming a dipole, with the negative end of the dipole of one molecule approaching the positive end of the dipole of another molecule. - Hydrogen bridge (H) - the strongest intermolecular force and a special type of permanent dipole. Hydrogen bridges occur when hydrogen atoms bond with highly electronegative elements such as fluorine, oxygen, or nitrogen in a molecule, forming a very strong dipole. Hydrogen protons are attracted to the negative regions of other similar molecules, forming a strong network of intermolecular bonds.

[0030] Using the above three intermolecular forces, the equation proposed by Hansen for the solubility parameter δ of a polar fluid is as follows:

[0031]

number

[0032] The Hansen solubility parameter distance D between a solvent and a polymer in the HANSEN solubility space is calculated by the following relationship:

[0033]

number

[0034] The higher the value of one of the solubility parameters, the higher the energy associated with the intermolecular interactions represented by that parameter and the higher the amount of energy required to separate the molecules.

[0035] The relative cohesive energy or relative energy difference (RED) is the ratio of the radius or distance D (which is the Hansen ratio) of the solubility parameter to the solubility parameter. RED=D / δ where RED<1 indicates high polymer solvent affinity; RED=1 indicates low polymer solvent affinity; RED>1 indicates that the solvent has no compatibility with the polymer.

[0036] Alternatively, this proposal also envisages the use of a "reactive solvent" in the aforementioned method as a decrosslinking agent and to promote swelling of the polymer matrix. Thus, within the scope of the present invention, the aforementioned "reactive solvent" consists of a component that simultaneously acts as a vehicle and as a decrosslinking agent. Thus, the "reactive solvent" is capable of generating the radicals necessary for decrosslinking in the presence of ozone.

[0037] In this context, a "reactive solvent" consists of a solvent having a RED of less than 1. Preferably, a "reactive solvent" is a solvent having the formula (I)

[0038] [ka] (In the formula, R is hydrogen or CH3, and R' is an alkyl group having 1 to 4 carbon atoms.) The compound is selected from the group consisting of acrylates or methacrylates represented by the formula:

[0039] FIG. 3 shows a proposed route for radical formation with styrene in the presence of ozone.

[0040] In order to achieve the above object, the present invention provides a method for recycling elastomers, comprising the steps of: 1) dissolving a stripping agent in a solvent and adding the solution thus formed to the solid elastomer waste; 2) stirring and then leaving the waste to stand for a period of time depending on the particle size of the waste; 3) adding water; and 4) Adding ozone The present invention provides a method comprising:

[0041] In a preferred embodiment, a method for chemical recycling of solid elastomer waste is proposed, which comprises: in step 1) dissolving about 0.5 to about 30 parts (per 100 parts of waste) of a decrosslinker in about 4 to about 10 parts (per 100 parts of waste) of a solvent and adding the formed solution to the elastomer waste, where the decrosslinker is selected from a peroxide or a persulfate and the solvent is selected from a halogenated organic solvent and / or an aromatic organic solvent; in step 2) stirring for about 30 minutes and allowing to stand for 1 hour to 24 hours; in step 3) adding up to 500 parts (per 100 parts of waste) of water; and in step 4) bubbling ozone at a flow rate of about 30 mg / L to about 50 mg / L for 4 hours to 6 hours.

[0042] Preferably, the peroxide is selected from the group consisting of benzoyl peroxide, dicumyl peroxide, oxybisperoxide, etc., or mixtures thereof, and the persulfate is selected from the group consisting of ammonium persulfate, potassium persulfate, sodium persulfate, etc., or mixtures thereof.

[0043] Alternatively, the present invention proposes a method for recycling elastomers via a "reactive solvent", in which the method is carried out in the presence of ozone and a "reactive solvent". In this context, the present invention provides a method for recycling elastomers, comprising: 1) preparing a solution containing water, a surfactant and a "reactive solvent" and adding the formed solution to solid elastomer waste; 2) stirring and then leaving the waste for a period of time depending on the particle size of the waste; 3) Adding ozone The present invention provides a method comprising:

[0044] In a preferred embodiment, a method for chemical recycling of elastomer waste is proposed, which comprises, in step 1), preparing a solution comprising up to 500 parts (per 100 parts of waste) of water, up to about 2.5 parts (per 100 parts of waste) of a surfactant and about 0.5-30 parts (per 100 parts of waste) of a "reactive solvent" and adding the formed solution to the elastomer waste, where the surfactant is preferably selected from the group consisting of sodium lauryl ether sulfate and ethoxylated nonylphenol; in step 2), stirring for about 30 minutes and allowing to stand for 1 hour to 24 hours; and in step 3), bubbling ozone at a flow rate of about 30 mg / L to about 50 mg / L for 4 hours to 6 hours.

[0045] The present invention also relates to recycled elastomers obtainable by the process proposed herein.

[0046] Furthermore, the present invention proposes the use of recycled elastomers in the manufacture of articles, said recycled elastomers being obtained by the process defined herein and replacing raw materials consisting of the respective virgin elastomers in a quantity of more than 60%. Furthermore, the present invention proposes the use of recycled elastomers obtained by the process defined herein as a complete replacement of the respective virgin elastomers, i.e. a 100% use of recycled elastomers. Furthermore, the present invention proposes the use of recycled elastomers obtained by the process defined herein to replace raw materials consisting of other polymers. In this context, the present invention envisages the use of recycled elastomers in the manufacture of articles, especially for the footwear, construction, automotive and white goods industries.

[0047] The presented examples are illustrative of the scope of the invention proposed herein. EXAMPLES

[0048] Tests have been carried out which show that the materials recycled by the chemical recycling method of the present invention have similar technical qualities as the corresponding virgin materials, and therefore there is compatibility and miscibility between the recycled materials and the initial polymer matrix.

[0049] [Example 1] Density, hardness and abrasion resistance Table 1 shows the results of density, hardness and abrasion resistance tests performed on a sample consisting of 70% by weight SBR and 30% by weight virgin SBR that was chemically recycled using the method of the present invention, using benzoyl peroxide as a decrosslinking agent, in comparison with a virgin SBR sample.

[0050] [Table 1]

[0051] As can be seen, the incorporation of recycled material did not affect the mechanical properties observed in the control sample (in fact, these properties were improved). Figure 4 shows the appearance of the test specimens made of virgin SBR and a blend of 30% virgin SBR and 70% recycled SBR according to the invention.

[0052] [Example 2] Modulus of elasticity, tensile strength at break, elongation and hardness Table 2 shows five samples of virgin polymer and polymer blends that were chemically recycled using the method of the present invention using benzoyl peroxide and ammonium persulfate as decrosslinkers and styrene as a "reactive solvent," along with the results of tests performed on each of the virgin polymers for modulus, tensile strength at break, elongation, and hardness (Shore A).

[0053] [Table 2]

[0054] The black EPDM used is composed mostly of EPDM resin (although it also contains blends with PE at filler concentrations below 25% by weight).

[0055] As can be seen, the incorporation of recycled materials did not affect the mechanical properties observed in the standard black EPDM samples (in fact, these properties were improved). The black EPDM materials exhibited inferior properties when compared to the same materials with a corresponding 70 wt. % recycled content, and also when compared to samples consisting of only recycled black EPDM material.

[0056] [Example 3] Differential scanning calorimetry (DSC) analysis Tables 3 and 4 show the parameters used and the results obtained in the DSC analysis carried out on samples consisting of solid SBR waste chemically recycled according to the method of the invention using benzoyl peroxide and ammonium persulfate as decrosslinking agents and styrene as "reactive solvent", respectively, compared with samples of solid SBR waste not subjected to these methods.

[0057] [Table 3]

[0058] [Table 4]

[0059] The decrease in Tg values ​​of the analyzed samples demonstrates the efficiency of the proposed decrosslinking mechanism. The obtained data confirm the increased mobility of the polymer matrix due to the reduction of intercrosslinks. It should be noted that the decrease in Tg shown by DSC is related to the destruction of crosslinks and not to the degradation of the polymer structure.

[0060] As can be seen from the above examples, the present invention makes it possible to realize an effective chemical recycling method for elastomers, without the need for high temperatures, special equipment or the use of compatibilizers, and for a wide variety of elastomers, regardless of their original vulcanization / crosslinking method. Moreover, the method allows recycling large batches of waste on a daily basis, using a relatively simple industrial plant. However, the present invention proposed here provides recycling residues that can largely replace virgin elastomers (virgin rubber) in the mixed composition of new vulcanized rubber-based articles, thus facilitating significant savings in terms of energy consumption and reducing the need to consume elastomeric materials from non-renewable resources. The proposed method is therefore comprehensive and versatile, allowing the same industrial plant to be used to recycle several types of sulfur- or peroxide-based elastomeric waste (e.g. crosslinked PE and PP, EPM, EPDM, EVA, SBR, etc.).

[0061] The more efficient decrosslinking reaction achieved by the method proposed herein allows the use of more than 60% recycled material, and depending on the article being compounded, up to 100% recycled elastomers can be compounded. Furthermore, recycled elastomers have the advantage of being highly compatible and miscible with the respective polymer matrix and in mixtures with other polymers.

Claims

1. A method for recycling elastomer waste, comprising the steps of: 1) dissolving a decrosslinking agent in a solvent and adding the solution thus formed to the elastomer waste, wherein the decrosslinking agent is selected from peroxides, persulfates, or the like or mixtures thereof; 2) promoting stirring, followed by settling; 3) adding water; and 4) Adding ozone A method comprising:

2. 10. The method of claim 1, wherein the amount of the decrosslinking agent is from about 0.5 to about 30 parts per 100 parts of waste.

3. 2. The method of claim 1, wherein the peroxide is selected from the group consisting of benzoyl peroxide, dicumyl peroxide, oxybisperoxide, etc., or mixtures thereof.

4. 2. The method of claim 1, wherein the persulfate is selected from the group consisting of ammonium persulfate, potassium persulfate, sodium persulfate, and the like, or mixtures thereof.

5. 2. The process according to claim 1, characterized in that the solvent is selected from the group consisting of halogenated or aromatic or similar organic solvents, or mixtures thereof.

6. 6. The method according to claim 5, characterized in that the solvent is toluene and / or xylene.

7. 10. The method of claim 1, wherein the amount of solvent is from about 4 to about 10 parts per 100 parts waste.

8. The method according to claim 1, wherein in step 2), the stirring is carried out for about 30 minutes and the standing is carried out for 1 hour to 24 hours.

9. 2. The method according to claim 1, characterized in that in step 3) the amount of water is up to 500 parts (per 100 parts of waste).

10. 2. The method of claim 1, wherein in step 4), ozone is bubbled at a flow rate of about 30 mg / L to about 50 mg / L for 4 hours to 6 hours.

11. A method for recycling elastomer waste, comprising the steps of: 1) preparing a solution comprising water, a surfactant and a decrosslinker and adding the formed solution to an elastomer residue, the decrosslinker being a "reactive solvent"; 2) promoting stirring, followed by allowing to stand; and 3) Adding ozone A method comprising:

12. 12. The method of claim 11, wherein the "reactive solvent" consists of a solvent having a RED of less than 1.

13. The "reactive solvent" is represented by the formula (I) 【Chemistry 1】 (Wherein, R is hydrogen or CH ３ and R' is an alkyl group having 1 to 4 carbon atoms.

13. The method according to claim 12, characterized in that the acrylate or methacrylate is selected from the group of acrylates or methacrylates of the formula:

14. The method of claim 11, wherein the amount of "reactive solvent" is from about 0.5 to about 30 parts per 100 parts of waste.

15. 12. The method according to claim 11, characterized in that the surfactant is preferably selected from the group consisting of sodium lauryl ether sulfate and ethoxylated or similar nonylphenols or mixtures thereof.

16. 12. The method of claim 11, wherein the amount of surfactant is up to about 2.5 parts per 100 parts of waste.

17. 12. The method according to claim 11, characterized in that the amount of water is up to 500 parts (per 100 parts of waste).

18. The method according to claim 11, wherein in step 2), the stirring is carried out for about 30 minutes, and the standing is carried out for 1 hour to 24 hours.

19. 12. The method according to claim 11, wherein in step 3), ozone is bubbled at a flow rate of about 30 mg / L to about 50 mg / L for 4 hours to 6 hours.

20. A recycled elastomer, characterized in that it is obtainable by the method according to claim 1.

21. A recycled elastomer, characterized in that it is obtainable by the method according to claim 11.

22. 12. Use of the recycled elastomer obtained by the method according to claim 1 or 11, characterized in that it replaces a part of the raw materials containing virgin elastomers for the manufacture of articles.

23. 23. Use according to claim 22, characterized in that it is for manufacturing articles for the footwear, construction, automotive or white goods industry.

24. 23. Use according to claim 22, characterised in that the amount of recycled elastomer used is 60% or more.

25. 23. Use according to claim 22, characterized in that it is a mixture with other polymers.

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