METHOD FOR THE DEVULCANISATION OF A VULCANISAED RUBBER MIXTURE, DEVICE FOR CARRYING OUT THE METHOD, AS WELL AS A RUBBER MIXTURE AND VEHICLE PNEUMATIC TYRE, COMPRISING A COMPONENT MADE OF THE RUBBER MIXTURE

Abstract

The invention relates to a process for devulcanizing a vulcanized rubber mixture, comprising the following steps: A) providing or producing a vulcanized rubber mixture, B) comminuting the vulcanized rubber mixture into a granulate of vulcanized rubber particles, C) extruding the vulcanized rubber particles produced in step B) in a twin-screw extruder to form a devulcanized rubber mixture, wherein, during the extruding in step C) at least one regeneration reagent is added to the extruded rubber particles, wherein the regeneration reagent comprises at least one silane, at least one plasticizer, at least one aging stabilizer or mixtures thereof. The invention also comprises an apparatus for performing the method and the uses of the apparatus, and a rubber mixture and also a pneumatic vehicle tyre or a technical rubber article comprising a component composed of the rubber mixture.

Claims

1.-15. (canceled)

16. A method for devulcanization of a vulcanized rubber mixture, the method comprising: A) producing a vulcanized rubber mixture; B) processing the vulcanized rubber mixture into a granulate of vulcanized rubber particles; C) extruding the vulcanized rubber particles produced in B) in a twin-screw extruder to form a devulcanized rubber mixture; adding at least one regeneration reagent to the extruded rubber particles, wherein the one regeneration reagent comprises at least one of a group comprising silane, a plasticizer, at least one aging stabilizer and mixtures thereof.

17. The method of claim 1, wherein the regeneration reagent comprises at least one plasticizer and at least one silane, comprises at least one aging stabilizer and at least one silane, comprises an aging stabilizer and at least one plasticizer, wherein the aging stabilizer is preferably selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol (BHT), 2,2′-methylene-bis(4-methyl-6-tert-butyl-phenol), 2,2′-methylene-bis(4-methyl-6-cyclohexyl-phenol), 2-mercaptobenzimidazole, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and methyl-2-mercaptobenzimidazole, comprises an aging stabilizer and at least one plasticizer and at least one silane, or comprises a resin, an aging stabilizer, at least one plasticizer and at least one silane, and/or comprises one or more plasticizers or consists of one or more plasticizers, wherein the one plasticizer or one of the two or more plasticizers or each of the two or more plasticizers are an oil having a content of polycyclic aromatics of more than 0.1% by weight, very particularly preferably polycyclic aromatics of in the range from 1% to 70% by weight, especially particularly preferably polycyclic aromatics of in the range from 10% to 40% by weight, in each case as determined by the IP346 method, selected from mild extraction solvents (IVIES), treated aromatic extracts of treated distillate (TDAE) and heavy naphthenic oils,

18. The method of claim 16, wherein the one regeneration reagent added during step C) is added in an amount in the range from 20% to 0.1% by weight, preferably in an amount in the range from 10% to 1% by weight, particularly preferably in an amount in the range from 6% to 3% by weight, in each case based on the sum of the mass of vulcanized rubber particles extruded in step C) and the mass of regeneration reagent added in step C), and the regeneration reagent comprises at least one silane and/or the total amount of silanes, which preferably comprise at least one disulfide or consist of one or more disulfides, in an amount in the range of less than 5% by weight, particularly preferably in an amount in the range of less than 1% by weight, very particularly preferably in an amount in the range of less than 0.1% by weight, especially particularly preferably comprises no silane whatsoever, in each case based on the sum of the mass of vulcanized rubber particles extruded in step C) and the mass of regeneration reagent added in step C).

19. The method of claim 16, wherein adding at least one regeneration reagent to the extruded further includes introducing a specific energy input of 0.01 to 5 kWh/kg into the vulcanized rubber particles based on the total mass of the vulcanized rubber particles extruded in step C), preferably 0.1 to 1 kWh/kg.

20. The method of claim 16, wherein adding at least one regeneration reagent to the extruded rubber particles includes holding the devulcanized rubber mixture at a temperature of 50° C. to 150° C. and pressing the extruded rubber particles through a filter unit comprising a sieve and a perforated plate, wherein the devulcanized rubber mixture is heated to a temperature of 50° C. to 150° C. on account of the pressing through the filter unit.

21. The method of claim 16, wherein during the extruding during the entirety of step C) the vulcanized rubber particles produced in step B) are extruded in the twin screw extruder at a shear rate of below 300 s.sup.−1, preferably at a shear rate in the range from 1 s.sup.−1 to 100 s.sup.−1, wherein the shear rates are particularly measured only at the screw elements which are conveying elements, and the temperature of the vulcanized rubber particles is below 200° C. and a devulcanized rubber mixture having a temperature of above 100° C. is formed, wherein the twin-screw extruder preferably has a length of less than 60 D.

22. The method of claim 16, wherein the average particle diameter of the rubber particles resulting in step B) is in the range from 0.01 mm to 50 mm, preferably in the range from 0.1 mm to 20 mm, and/or the proportion of the processed rubber particles resulting in step B) that passes through a 44 mesh sieve in a sieve test according to Japanese industrial standard JIS P-8207 is at least 50% by weight of the total mass of processed rubber particles resulting in step B), preferably at least 80% by weight of the total mass of processed rubber particles resulting in step B), wherein the vulcanized rubber particles resulting in step B) have a maximum particle diameter of 100 mm.

23. An apparatus for devulcanization of a vulcanized rubber mixture, the apparatus comprising: a twin-screw extruder having a length of less than 60 D and having a feed unit for feeding a regeneration agent; the feed unit adapted for introducing the regeneration reagent at a point on the upper half of an inner wall of an extruder barrel of the twin-screw extruder; and the twin-screw extruder configured to form a devulcanized rubber mixture.

24. The apparatus of claim 23, further comprising: a further kneading unit arranged downstream of the twin-screw extruder which comprises a single-screw extruder and a gear pump for producing rubber mixtures; a filter unit comprising a sieve; and a particle comminution for comminuting a vulcanized rubber mixture to a granular material composed of vulcanized rubber particles having a maximum particle diameter of 100 mm and/or having an average particle diameter in the range from 0.1 mm to 20 mm.

25. The apparatus of claim 24, wherein the apparatus comprises a mixer arranged downstream of the one twin-screw extruder for producing the rubber mixture comprising the extrudate from the one twin-screw extruder and a forming unit arranged downstream of the one mixer for forming an unvulcanized tire body component.

Description

EXPERIMENTAL EXAMPLES

Test Methods:

[0140] 1. Mooney Viscosity [0141] The results were determined at 100° C. (in Mooney units M.U.) on the basis of the method of DIN 53523 (ML1+3).

[0142] 2. Breaking Elongation [0143] The results were determined at room temperature on the basis of the method of DIN 53504 [units: %].

[0144] 3. Fatigue-to-Failure Test (“Monsanto Fatigue Test”) [0145] The results were determined at 106% elongation and room temperature on the basis of the method of ASTM D4482. The results were reported in units of kilocycles (kC for short).

Production of the Devulcanizates V1, E1 and E2:

[0146] Initially, old truck tires were comminuted in a particle comminution unit to afford a granulate of vulcanized rubber particles having a maximum particle diameter of 100 mm and having an average particle diameter in the range from 0.1 mm to 20 mm.

[0147] Production of the devulcanizates according to the invention from this granulate was carried out in a twin-screw extruder comprising an extruder barrel having a horizontally oriented extruder barrel having a length of less than 60 D, wherein the one twin-screw extruder comprised a feed unit for feeding a regeneration reagent and the regeneration reagent was at a point above the extruder barrel introduced vertically downwards into the extruder barrel of the one twin-screw extruder. The process for devulcanization of the produced vulcanized rubber particles comprised the following step C): [0148] C) extruding the produced vulcanized rubber particles in a twin-screw extruder comprising an extruder barrel having a length of less than 60 D,
wherein during the extruding in step C) an amount of regeneration reagent according to table 1 is added to the extruded rubber particles, wherein the regeneration reagent comprises [0149] a plasticizer and no silane (devulcanizate E1)
or [0150] a plasticizer with aging stabilizer but no silane (devulcanizate E2),
wherein [0151] during the extruding in step C) the screw speed of the screws of the twin-screw extruder is 200 rpm and during the extruding in step C) the vulcanized rubber particles are extruded in the twin-screw extruder at a shear rate of below 300 s.sup.−1, [0152] during step C) the temperature of the vulcanized rubber particles is in the range from 140° C. to 160° C. and [0153] in a temperature control step D) carried out subsequently to step C) the devulcanized rubber mixture is heated to a temperature of 50° C. to 150° C. for 10 minutes.

[0154] For the comparative vulcanizate V1 no regeneration reagent was added during the extruding. The production parameters otherwise remained the same.

TABLE-US-00001 TABLE 1 V1 E1 E2 Constituents Unit (comp.) (inv.) (inv.) vulcanized rubber particles % by wt. 100 92.5 94.5 TDAE % by wt. — 5.5  5.5 Aging stabilizer 6PPD* % by wt. — 2 — *6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (CAS No.: 793-24-8)
Production of the exemplary mixtures VB1, EB1 and EB2:

[0155] The inventive and noninventive devulcanizates were each mixed in a mixer with further constituents according to the following table 2 to obtain the inventive and noninventive rubber mixtures VB1, EB1 and EB2. The resulting rubber mixtures VB1, EB1 and EB2 were then cut into a cut-to-size unvulcanized test component in a forming unit and subsequently vulcanized to afford a test component. The forming unit comprised an extruder with a preliminary and final template for forming an unvulcanized component and a downstream cutting unit for cutting the unvulcanized component into the intended shape for testing the breaking elongation or the “fatigue-to-failure” values.

TABLE-US-00002 TABLE 2 Name: Mixing VB1 EB1 EB2 Constituents: Unit stage Non-inv. Inv. Inv. NR phr 1 25 25 25 BR phr 1 50 50 50 SBR phr 1 25 25 25 Devulcanizate V1 phr 1 28 — — Devulcanizate E1 phr 1 — 28 — Devulcanizate E2 phr 1 — — 28 Carbon black phr 1 40 40 40 Plasticizer phr 1 5 5 5 Aging inhibitor phr 1 2 2 2 Stearic acid phr 1 2 2 2 ZnO phr 1 3 3 3 Sulfur phr 2 1.5 1.5 1.5 Vulcanizing agent phr 2 1.5 1.5 1.5 Unit VB1 EB1 EB2 Chemical properties of the mixtures before vulcanization Mooney viscosity M.U. 55 49 51 Physical properties of the mixtures before vulcanization Breaking elongation % 449 456 469 Fatigue-to-failure test kC 66.9 >2000 >2000

[0156] As is apparent from table 2 the vulcanizates of the rubber mixtures EBI and EB2 which contain the inventive devulcanizates E1 and E2 exhibit much higher and thus much better values in the fatigue-to-failure test than rubber mixtures such as VB1 which contain the devulcanizate V1 known from the prior art. No cracks which would have lead to test termination were determined even after 2 million cycles (i.e. >2000 kC). This is an unexpected technical effect. This is unexpected especially because the values in the measurement of breaking elongation differ from one another only minimally.

[0157] The rubber mixtures BE1 and BE2 exhibit a comparatively higher Mooney viscosity relative to the mixture VB1. The Mooney viscosity generally shows that the rubber mixtures are more readily processable and that process reliability increases for the inventive mixtures.