PROCESS FOR REGENERATING VULCANIZED RUBBER

Abstract: Process for the regenerating of vulcanized rubber, using the combined action of a solvent which has the property of swelling the vulcanized rubber and a material which is deleterious or devulcanizing. As adequate swelling agents for the carrying out of the process, consideration should be given particularly to benzine, toluene, xylene or a mixture of these, as also cyclic and halogenized parafinic solvents. As deleterious material, adequate for the reduction in size of the elastomere particles, the following metals should be considered: copper, manganese, iron, chrome, nickel and cobalt, as well as their alloys and derivates. Adequate devulcanizing agents for use in the present invention are the derivates of guanadine, the derivates of hydrazine and the derivates of phenylhydrozilamine. By the process of the invention, a regeneration of excellent quality is obtained, working at normal temperature and pressure, although an increase of these variables will give a reduction in the time of the operation.

Description: Descriptive report of the Invention Patent for a "PROCESS FOR REGENERATING VULCANIZED RUBBER". This invention refers to a process for regenerating vulcanized rubber, utilising the capacity which this product has of absorbing solvents, as also of its being sensitive to the action of certain- deleterious chemical products. The use of regenerated rubber in comparison with raw rubber results in less expenditure for industry, due to the fact that, in many cases, the price of the regenerated product is less than half that of raw rubber. In addition to this, regenerated rubber may be used to advantage, where some characteristics of the final product need to be brought out, or where it is desired to optimize certain operating conditions. The following may be quoted as advantages: low therntσplasticity, rapid processing, short mixing time and, further, the use of the regenerated product as a substitute in the usual ingredients used in the composi¬ tion of rubber- In the ruber industry, the use of a large part of the product to be regenerated has its origin in the milling of the used products, or scrapings of tyres for retreading-. In the milling of the used products, normally after separaation of the metallic parts, the vulcanized product is passed once or twice through the mincing mills, which reduce the product into little pieces. This material is then homogenized, by passing it through sieves and is left in a state similar to the scrap¬ ings of tyres for retreading. Both in the milling and in the ' use of the scrapings of the tyres, after sieving, the material held by the sieve, is returned to the mill for a .. new mincing. The best known processes .for reducing vulcan ' i-zed rub¬ ber to little pieces, or even to reduce the pieces already mil¬ led and homogenize them, are: - a cylinder mill, with or without grooves; - a disc mill; and - a hammer mill, at low temperatures, . (for example using liquid nitrogen directly, or freon indirect¬ ly ) . All thesethree processes have their limitations in relation to the granulation of the product obtained, though the process which uses the hammer mill at low temperatures is the one which produces the finest powder. However, the out¬ put is low, which makes the process very expensive, when it is desired to reduce the particles to the utmost. Depending on the final characteristics ofthe rubber mixture, it is often necessary to use very fine powder. The finer it is, the better is the compatibility of the powder with, the elastomere and, better also in relation to other qualities, such as resistance to abrasion; module: hardness, thus becoming a strengthening force. In any case, in some regenerating processes, it is necessary to use a fine powder, which facilitates the action of the chemical and physical agents. Up to the present moment, techniques have not resolved all the problems connected with the pulverizing and regene- ration of vulcanized rubber. In patent GB 1334718, a process is described for pul¬ verizing ruber, which includes subjecting the fragments of this material to a temperature of less than - 40°-C, by means _ - of cryogenic agents, to facilitate the separation of the rubber from the remaining constituents of the composition, including the metallic components.. After the separation has been made, there is a conventional pulverization process, such as the use of a hammer or other mill. Although the separation of the constituents is thus facilitated, this process has the incon- venience of operating at excessively low temperatures and using a great deal of liquid nitrogen. In accordance with Patent US 2088920, a process is described for the regenerating of rubber, using derivates of guanidine, which have devulcanbizing properties. For an ade- quate mixture to be made as between the devulcanizer and the rubber, the latter should be finely divided. However, in this patent, there is no description of the specific pulverization proces-s which should be used. In Patent US 4156508, a mechanical process is des¬ cribed, using pressure and hig temperatures and and passing through a refiner to reduce and regenerate the particles of vul canized rubber, giving a regenerated product with a Shore hardness of between 50 and 62. The inconvenience of this pro¬ cess lies in the use of the power to keep up the temperature and the need for high pressures. In accordance with request BR 7606727, a process is described for the recovery and re-use of ellastomeric vulca¬ nized material, which involves the raising of the temperature on the surface of the material to between 2000 and 3000°-C for a brief period of from 1 to 10 seconds. In Patent GB 505156, a method is described for the pulverizing of remains of vulcanized rubber, such objective being achieved by a continuous process, which basically, in¬ volves the following steps: 1st) impregnation of the material to be pulverized, with an intumescent agent; and 2nd) submitting the material to the mechanical action of a mill so as to reduce the residue to a fine powder and se¬ parate the other constituents of the composition from the rubber. ' In accordance with this patent, any adequate intu- mescing agents may be used, preferablynon-inflammable, chlo- rated organic solvents. However, in this patent, no practical examples are given in which the efficiency of the process can be checked and the characteristics of the pulverization. The present invention is for an integral regenera¬ tion of vulcanized rubber, from which a final product with ex¬ cellent qualities emerges. More specifically, the present invention refers to a process for the regeneration of vulcanized rubber, character¬ ized by the initial intumescing (swelling) of the rubber with an organic solvent and the subjecting of this material to a treatment with a deleterious or devulcanizing agent. The utilization of a material which reduces the size of the elastomere particles in a reduction process in combi¬ nation with an intumescent agent, provides the intrinsic ad¬ vantage of being able to work in normal temperature and pres¬ sure conditions, whilst still obtaining a product of excel- lent quality. For the purpose of the present invention, the follow¬ ing should be regarded as materials adequate for the reduction of the size of the elastomere particles: copper, manganese, iron, chrome, nickel and cobalt as well as their respective alloys and derivates. The effect of these metals in the breaking uup ofr the structure of the ruber is described in request BR-7905590, incorporated hereto by way of reference. As adequate intumescent agents for use in the present invention, benzine, toluene, xylene or a mixture of these should be considered, as well as cyclic and halogenated para- ffinic solvents. The intumescing agent should be present in such quan¬ tity that it be sufficient to provide swelling of the elasto- mere from 1 to 8 parts by weight of the solvent to each part of the elastomere. Preferentially, 5 to 7 parts of the sol¬ vent to each part of the elastomere should be used, though the use' of excessive solvent does not create substantial problems in the ca rying out of the invention, since it should be fully recovered. The devulcanizing agents which should be used in the present invention are: the derivates of guanadine, for example; diphenylguanadine, derivates of hydrazine, for example phenylhydrazine and the derivates of phenyla ine, for exampl anilyne. The devulcanizing agent should be present in th range of 0.2 to 3% of the elastomere-, preferably around 1% The length of tie the elastomere should be in con tact with the intumescent and the devulcanizer is in relatio to the type of elastomere used, the quantity of the intumesc ing agents and the devulcanizing agent. The use of pressure and temperature facilitate no on'Cy the swelling action, but also the action of the deleteri ous and devulcanizing agents, and can thus reduc e the time fo the regeneration. However, it must be understood that, fo the purpose of the present invention, the use of temperatur and of pressure are variants of the process in question. The advantages inherent to the process of the inven tion will become evident from the examples presented below. It will be obvious to those who work in the area that the con¬ ditions are as easy as possible and that the regenerated pro¬ duct -may be used in a subsequent processing. These examples have as their object the presenting of practical aspects of the process of rubber regeneration with¬ out however, their being considerd to be limitative in relation to the definition of the invention. Where there is no reference to the units of measure for the ingredients employed, it should be taken that they are parts by weight. Basic r-iaterial The material which served as the basis for the fol¬ lowing tests was prepared. Basic formulation of ground material: SBR - 1500 -100.o Zinc Oxide - 3.o Stearic Acid - 2.o Carbon Black N-330 - 65.o Aromatic Oil - 8.o Cumarona-indeno resin -. l.o Antioxidant *1 - l.o Accelerator *2 - l.o Activator *3 - o.5 Sulphur - 2.o NOTE: Antioxidant - N-phenyl-N-cyclohexyl- p-phenylenediamine. Accelerator - Disulphatelphide of mer- captobenzothyazyl. Activator - Diphenylguanidine. The mixture was vulcanized for 45 minutes at a tem¬ perature of 150 2 C and a material was obtained of the following characteristics: - Breaking load (kg/cπt ) -160 - Module at 300% (kg/cm ) - 81 - Stretching (%) -550 - Hardness (Shore A) - 70 - Abrasion (Standard) (%) .-100 - Acetonic Extract (%) - 6 - Chloroformic Extract (%) - — The material was cut into strips and passed through the cylinder grinder until it became very small ' pparticles, for the tests which follow below. EXAMPLE 1 - outside the scope of the invention. 150g of the basic material was taken, mixed with 0.15g of regenerator of the Penta-chloro-thyophenol type and 15 g of aromatic oil, placed in a wet autoclve for 6 hours, at a pres- 2 sure of 15.5 kg/cm , at 210 2 C The resulting material was re¬ fined and a mixture with formula Standard A was made. Basic Material - 100.o Formula Standard A - 15.5 Zinc Oxide - (0.3) Stearic Acid - (0.2) Aromatic Oil - (0.6) Antioxidant 1 - (0.1) Accelerator 2 - (0.1) Activator 3 - (0.5) Sulphur - (2.0) (*) Formula Standard A Characteristics of the material vulcanized at 150 2 C for 45 minutes: Breaking load ( kg/cm 2 ) - 70 Module 300% ( kg/cm 2 ) - 35 Stretching ( % ) -500 Hardness ( Shore A) -553 Abrasion ( %') - 30 Acetonic Extract ( % ) - 20 Chloroformic Extract ( % ) - 18 ' EXAMPLE 2 150g of the basic material was taken and allowed to swell in 1000ml of benzine for two days. It was then placed in a ball mill and beaten for 20 hours with 2g of manganese powder. Subsequently, 200 ml of sulphuric acid 0.1N were added and.'the systems beaten for four hours. At the end of this time the material was neutralized, washed, dried and ho¬ mogenized in an open mixer and used in a mixture with formula Standard A. Material of Example 3 -100.o Formula Standard A - 15.5 The characteristics of the material after being vul¬ canized at 150 2 C for 45 minutes are shown in Table 1. EXA MPLE 4 150g of the basic material was taken and allowed to swell in lOOOml of benzine for two days. It was then placed in a ball mill and beaten for 20 hours with 50ml of copper chloride IN. Subsequently the material was washed, dried, ho¬ mogenized in a mixer and used in a mixture with Formula stand¬ ard A, in the same proportion as the preceding cases.. The characteristics of thematerial vulcanized at 150 2 C for 45 minutes are given in Table 1. EXAllPLS 5 The same procedure was used as for Example 4, except that instead of using 50 ml of copper chloride, 50ml of man¬ ganese sulphate IN Uere used. EXAUPLE 6. 150g of the basic material was taken and allowed to swell in lOOOml of toluene for two days. It was then placed in a bronze ball mill and beaten for 20 hours. Subsequently the material was dried, homogenized in an open mixer and used in a mixture with Formula Standard A, in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150 2 C for 45 minutes are shown in Table 1. EXAMPLE 7. 150g of the basic material was taken and allowed to swell in xylene for two days. It was then placed in a ball mill (with a manganese content) and beaten for 20 hours. Subse quently the basic material was dried, homogenized in an open mixer and used in a mixture with Formula Standard A, in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150 C for 45 minutes is shown in Table 1. EXAMPLE 8 -. 150g of the basic material was taken and allowed to swell in lOOOml of xylene for 18 hours. The material was then placed in an iron ball mill and beaten for 18 hours, when 1.5g of diphenyl guandine was added and it was beaten for another 2 hours. Subsequently 2g of ferric chloride was added and it was beaten for a further two hours. The material was then dried, homogenized in an open mixer- and used in a mixture with Formula Standard A, in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150 2 C for 45 minutes are given in Table 1. EXAllPLE 9. 150g of the basic material was taken and allowed to swell in lOOOml of BTX for 18 hours. It was placed in an iron ball mill and beaten for 16 hours. 1.5g. of Diphenyl- hydrazine hydrochlorate was added and beaten for another hour.. Then ferric chloride was added and beaten for a further 30 minutes. . The material was then dried, homogenized in an open mixer and a mixture made with Formula Standard A in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150 2 C for 45 minutes are given in Table 1. EXAMPLE 10. 150g of the basic material was taken and allowed to swell in lOOOml of BTX for 14 hours. It was then placed in an iron ball mill and the material beaten for 16 hours. lOg . of aniline were added and it was beaten for another hour. Sub¬ sequently 5g. of sulphuric acid (d=1.84) and beaten for two hours.- It was then washed, dried, homogenized in an open mixer and a mixture made with Formula Standard A in the same propor- tion as in the preceding examples. The characteristics of the material vulcanized at 150 C for 45 minutes are shown in Table 1. 10. EXAMPLE 11. 150g. of the basic material was taken and allowed to swell in lOOOml of BTX for 12 hours. .It was then placed in a bronze ball mill with 30g of highly aromatic plastifying oil and beaten for 18 hours. The material was then dried, homo¬ genized in an open mill and a mixture made with Formula Standar A in the same proportions as in the preceding examples. The characteristics of the material vulcanized at 150 2 C for 45 minutes are given in Table 1. EXAϋPLE 12. 150g. op the basic material was taken and allowed to swell in lOOOml of BTX and 30g of asphalt for 10 hours. It was then placed in a ball mill and beaten for 18 hours. The material was then dried, homogenized in an open mixer and a mixture made wit'l. Formula Standard A, in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150_ C for 45 minutes are shown in Table 1. EXAMPLE 13. 150g. of the basic material was taken and allowed to swell with lOOOml. of xylene for 6 hours at a temperature of 80 2 C. It was then placed in a bronze ball mill and beaten for 6 hours. The material was then dried, homogenized in an open mixer and a mixture made with Formula Standard A, in the same porportion as in the preceding examples. •TheKcharacteristics of the material vulcanized at 150 '2 C for 15 minutes, are given in Table 1. EXAllPLE 14. 150 2 C of the basic material was taken and allowed to swell with lOOOml of dichloroethane for 6 hours at a tempera¬ ture of 80 2 C. It was cooled to 20^ and put through a disc mixer, with cooling. It was recycled only for 30 minutes. It was then dried, homogenized in an open mixer and a mixture made with Formula Standard A, in the same proportions as in the preceding examples. The characteristics of the material vulcanized at 150 2 C. for 15 minutes are given in Table 1. EXAMPLE 15. 150g. of the basic material was taken and allowed to swell with lOOOml of dichloroethane for 6 hours at a tempera¬ ture of 80 2 C. It was cooled to 30 2 C. and passed through a hammer mill, being recycled for 30 minutes. I was then dried, homogenized in an open mixer and a mixture made with Formula Standard A, in the same proportion as in the preceding examples. The characteristics of the material vulcanized at 150 2 C. for 15 minutes, are given in Table 1.. TE SHEET TABLE 1 .ι j j

Claims: C L A I S 1. A process for the- regeneration of vulcanized rubber, characterised by involving the initial swelling of the rubber with an organic solvent and the subjecting of this a- terial to treatment with a deleterious or devulcanizing agent. 2. a process according to claim 1. characterized by the fact that the deleterrious material used is a metal as well as its alloys and derivates, chosen from the follow¬ ing constituents: copper, manganese, iron, nickel, chrome and cobalt. 3. A process according to claim 2. characterized by the fact that copper or manganese is employed. 4. A process according to claim 3 characterized by the fact that copper is employed. 5. A process according to claim 1. characterized by the fact that the organic solvent is benzine, toluene, xylene or another aromatic solvent or a mixture of these, or cyclic and halogenized paraf'lnic solvents. 6. A process according to claim 5. characterized by the fact that the organic solvent employed is an aromatic derivate such as benzine, toluene, xylene or their mixtures. 7. A process according to claim 1, characterized by the fact that the organic solvent is to be employed in a quantity , relationship of 1 to 8 parts by weight, of the elas- tomere. 8. A-process in accordance with claim 7, character¬ ized by the fact of the organic solvent being employed in a quantity of 6 to 7 parts by weight per part of the elasto¬ mere. 9. A process according to claim' 1 1, characterized by the fact of the employment as a devulcanizing agent, a derivate of guanadine, a derivate of hydrazine or anilene. 10. A process according to claim 9, characterized by the fact that the derivate of -guanadine is diphenyl- guanadine. - O- ll. A process according to claim 9, characterized by the fact of there being employed as a devulcanizing agent an oxidant selected from a group of the derivates of iron, nickel, copper or managanese. 12. A process according to claim 9, characterized by the fact that the deveulcanizing agent is employed in a quantity of 0.2 to 4% by weight of the elastomere.

Inventors: OLIVEIRA DA CUNHA LIMA LUIZ CA, OLIVEIRA DA CUNHA LIMA, LUIZ, CARLOS
Applicants: OLIVEIRA DA CUNHA LIMA LUIZ CA, OLIVEIRA DA CUNHA LIMA, LUIZ, CARLOS
Application year: 1986
Main classification: C08J11
IPC codes: C08J11