Rubber formulation

Abstract

A method for manufacturing micronized rubber powders including grinding of a rubber granulated feedstock, size classification and storage of the micronized rubber powders thus obtained. A rubber formulation including at least one natural or synthetic rubber, a micronized rubber composition and optionally one or more of processing aids, antidegradants, fillers, accelerators and curatives. A method for manufacturing a rubber product, as well as to a solid rubber product.

Claims

1. A method for manufacturing micronized rubber powders comprising grinding a rubber granulated feedstock to obtain micronized rubber powders, classifying the micronized rubber powders by size, and storing the micronized rubber powders wherein during the grinding process an agent is used to prevent particles of the micronized rubber powders from sticking to themselves, wherein the agent is chosen from the group of synthetic amorphous precipitated silica and silane-treated synthetic amorphous precipitated silica, or a combination thereof wherein the grinding process of the rubber granulated feedstock comprises a two-step grinding process including ambient grinding followed by cryogenic grinding, and wherein the particle size of the rubber granulated feedstock after the ambient grinding is 0.1-0.8 mm.

2. The method according to claim 1, wherein the total amount of the agent is in a range of 0.1-4.0 wt. % based on the total weight of the micronized rubber powders.

3. The method according to claim 1, wherein the agent is in a fluffy state and the BET surface area of the agent is between 50 and 250 m.sup.2/g.

4. The method according to claim 1, wherein the agent is silane-treated synthetic amorphous precipitated silica.

5. The method according to claim 1, wherein the cryogenic grinding is carried out in a range of 40 to 80 C. for a rubber granulated feedstock comprising natural rubber and in a range of 20 to 60 C. for a rubber granulated feedstock comprising natural rubber and styrene-butadiene rubber.

6. The method according to claim 5, wherein the particle size of the rubber granulated feedstock before the grinding process is 2-5 mm.

7. The method according to claim 1, wherein the rubber granulated feedstock is chosen from the group of natural rubber, synthetic polyisoprene rubber, high cis-1,4-polybutadiene rubber, medium vinyl polybutadiene rubber, high vinyl polybutadiene rubber, emulsion styrene-butadiene rubber, solution styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, butyl rubber, chlorobutyl rubber, bromobutyl rubber, polynorbornene rubber, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), nitrile rubber, carboxylated nitrile rubber, polychloroprene rubber (neoprene rubber), polysulfide rubbers, polyacrylic rubbers, silicone rubbers, chlorosulfonated polyethylene rubbers, and various mixtures thereof.

8. The method according to claim 1, wherein said size classification provides at least two micronized rubber powders product streams, comprising an 80 mesh stream and a 40 mesh stream.

9. The method according to claim 8, wherein at least one of the 80 mesh micronized rubber powders product stream and the 40 mesh micronized rubber powders product stream is contacted with an agent chosen from the group of synthetic amorphous precipitated silica, silane-treated synthetic amorphous precipitated silica, organosilane and organic peroxide, or a combination thereof for obtaining an activated micronized rubber powder product.

10. A rubber formulation comprising at least one natural or synthetic rubber, a micronized rubber powder obtained according to claim 1 and optionally one or more of processing aids, antidegradants, fillers, accelerators and curatives, wherein said rubber formulation comprises at least one activation component chosen from the group silane, NR latex, organic peroxides, polyoctenamer, curatives, polyethylene wax, emulsion styrene butadiene rubber (eSBR), liquid acrylonitrile butadiene rubber (NBR), zinc oxide and colloidal sulphur.

11. The rubber formulation according to claim 10, wherein the amount of the activation component(s) is in a range of 2-20 wt. %, based on the total weight of the rubber formulation.

12. The rubber formulation according to claim 10, wherein the activation component is silane.

13. The rubber formulation according to claim 12, wherein the amount of silane is in a range of 1-10 wt. % based on the total weight of the rubber formulation.

14. The rubber formulation according to claim 10, wherein the activation component is a combination of silane and NR latex.

15. The rubber formulation according to claim 14, wherein the amount of silane is in a range of 5-9 wt. and the amount of NR latex is in a range of 4-8 wt. %, based on the total weight of the rubber formulation.

Description

DETAILED DESCRIPTION

(1) Three main technologies focusses on circular EOL tyre objectives; namely pyrolysis (recovered carbon black/oil/gas), devulcanisation and MRP. Global initiatives have been ongoing for many decades and continue today at an accelerated pace due to the global warming crisis and the negative impacts that tyre production has on the environment. Each of the three technologies presents its own set of challenges that need to be overcome before large scale re-use in new tyres will be possible.

(2) Specifically regarding MRP the main limiting factors restricting large-scale re-use in tyres are twofold:

(3) 1. Size reduction is limited due to energy efficiencies and certain technological limitations to about 180 microns (D95 percentile) 2. Low surface energy (powders do not effectively co-vulcanize into the new tyre compounds because there are no active chemical groups on the surface of the powder to create chemical crosslinks/covalent bonds) The net effect of these limiting factors is that the addition of small percentages (2-6 wt. %) of MRPs into new tyre compounds yields unacceptably low mechanical reinforcement (particularly with regards to tear strength and abrasion resistance). Additionally the dynamic performance of compounds containing MRP is compromised, manifesting in an increased tan delta value and Payne effect, leading to an increase in hysteresis, heat build-up and rolling resistance of the tire. This reduces the fuel efficiency of a tyre.

(4) An object of the present invention is to develop a method for chemically activating/functionalizing MRP.

(5) Another object of the present invention is to develop a method for manufacturing micronized rubber powders.

(6) Another object of the present invention is to develop a method and engineer an industrial process for upscaling to large volumes of functionalized MRP (8-10 ktons/year).

(7) Another object of the present invention is to develop a method for converting functionalized MRP into a solid strip or slab whilst retaining performance and dispersibility.

(8) The present invention thus relates to a method for manufacturing micronized rubber powders comprising grinding of a rubber granulated feedstock, size classification and storage of the micronized rubber powders thus obtained, wherein during the grinding process an agent is used to prevent the rubber powder particles sticking to themselves, wherein the agent is chosen from the group of synthetic amorphous precipitated silica and silane-treated synthetic amorphous precipitated silica, or a combination thereof.

(9) The present inventors found that by incorporating such an agent into a method for manufacturing micronized rubber powders one or more objects are achieved. The present inventors found that reactivation of the vulcanization potential of the MRP by chemical treatment can significantly improve both the mechanical and dynamic performance of MRPs in rubber compounds, thereby opening the door to large scale re-use within the tyre and TRG sectors. Such a contact step can be seen as first stage activation.

(10) In an embodiment of the method for manufacturing micronized rubber powders the total amount of the agent is a range of 0.1-4.0 wt. %, preferably of 0.3-1.5 wt. %, based on the total weight of the micronized rubber powders.

(11) In an embodiment of the method for manufacturing micronized rubber powders the agent is in a fluffy state and the BET surface area of the agent is between 50 and 250 m.sup.2/g, preferably between 140 and 190 m.sup.2/g.

(12) In an embodiment of the method for manufacturing micronized rubber powders the agent is silane-treated synthetic amorphous precipitated silica.

(13) In an embodiment of the method for manufacturing micronized rubber powders the grinding process of the rubber granulated feedstock comprises a two-step grinding process, namely a) ambient grinding followed by b) cryogenic grinding, wherein especially step b) is carried out in a range of 40 to 80 C. for a rubber granulated feedstock comprising natural rubber and in a range of 20 to 60 C. for a rubber granulated feedstock comprising natural rubber and styrene-butadiene rubber.

(14) In an embodiment of the method for manufacturing micronized rubber powders the particle size of the rubber granulated feedstock before the grinding process is 2-5 mm.

(15) In an embodiment of the method for manufacturing micronized rubber powders the particle size of the rubber granulated feedstock after a) ambient grinding is 0.1-0.8 mm.

(16) The rubber granulated feedstock is chosen from the group of natural rubber, synthetic polyisoprene rubber, high cis-1,4-polybutadiene rubber, medium vinyl polybutadiene rubber, high vinyl polybutadiene rubber, emulsion styrene-butadiene rubber, solution styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, butyl rubber, chlorobutyl rubber, bromobutyl rubber, polynorbomene rubber, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), nitrile rubber, carboxylated nitrile rubber, polychloroprene rubber (neoprene rubber), polysulfide rubbers, polyacrylic rubbers, silicone rubbers, chlorosulfonated polyethylene rubbers, and various mixtures thereof.

(17) In an embodiment of the method for manufacturing micronized rubber powders the step of size classification provides at least two micronized rubber powders product streams, comprising an 80 mesh stream and an 40 mesh stream.

(18) In an embodiment of the method for manufacturing micronized rubber powders at least one of the 80 mesh micronized rubber powders product stream and the 40 mesh micronized rubber powders product stream is contacted with an agent chosen from the group of synthetic amorphous precipitated silica, silane-treated synthetic amorphous precipitated silica, organosilane and organic peroxide, or a combination thereof for obtaining an activated micronized rubber powder product, preferably an organosilane polysulphide type or disulfide type. Such a contact step can be seen as second stage activation.

(19) The present invention also relates to a rubber formulation comprising at least one natural or synthetic rubber, a micronized rubber powder obtained as discussed above and optionally one or more of processing aids, antidegradants, fillers, accelerators and curatives, wherein the rubber formulation comprises at least one activation component chosen from the group silane, NR latex, organic peroxides, polyoctenamer, curatives, polyethylene wax, emulsion styrene butadiene rubber (eSBR), liquid acrylonitrile butadiene rubber (NBR), zinc oxide and colloidal sulphur.

(20) The principle of surface activation is to form chemical crosslinks between the vulcanized MRP and unvulcanised rubber compound during vulcanization of the new rubber product. The powders no longer exist as discrete and disruptive particles in the new compound matrix, instead they become an integral (bonded) part of a much more homogenous matrix. The surface activation can be achieved, for example, by coating the surface of the powder with a crosslinkable (unsaturated) polymer together with certain vulcanization chemicals such as zinc oxide, stearic acid, sulphur and organic accelerators. The surface treatment can be applied, for example, by a continuous extrusion or continuous powder drying process. An extrusion or milling process would convert the powder into a solid strip or slab. Such a process would have the advantage of converting a low bulk density powder to an extruded solid form (e.g. strip, sheet) where the powder particles become bound together by the new polymer(s) and other process additives. Furthermore, conversion of low bulk density powder to a solid material will almost triple the bulk density of the powder (from 400 kg/m.sup.3 to 1150 kg/m.sup.3) thereby facilitating efficient transportation and avoiding expensive powder bagging costs.

(21) In an embodiment of a rubber formulation the amount of the activation component(s) in the rubber formulation is more than 2 wt. % and lower than 20 wt. %, based on the total weight of the rubber formulation.

(22) In an embodiment of a rubber formulation the activation component is silane.

(23) In an embodiment of a rubber formulation the amount of silane in the present the rubber formulation is more than 1 wt. % and less than 10 wt. %, based on the total weight of the rubber formulation.

(24) In another embodiment of a rubber formulation the activation component is a combination of silane and NR latex.

(25) In such an embodiment of a rubber formulation the amount of silane in the present rubber formulation is more than 1 wt. % and less than 10 wt. %, preferably 5-9 wt. and the amount of NR latex in the present the rubber formulation, after drying, is in a range of 4-8 wt. %, based on the total weight of the rubber formulation.

(26) As discussed above, the present invention relates to a method of preparing a rubber formulation as discussed above, the method comprising: subjecting the at least one natural or synthetic rubber, the micronized rubber composition and optionally one or more of processing aids, and the at least one activation component to shear at temperatures less than 100 C. such that surface activation of the at least one natural or synthetic rubber is achieved.

(27) In an embodiment of the present invention the method further comprises extruding the surface activated rubber formulation into a slab.

(28) For some applications the extruded solid material can be directly vulcanized into moulded applications.

(29) A method for manufacturing micronized powders comprises several process steps, such as pre-grinding processing, cryogenic freezing, grinding of infeed material, resultant warming, ferrous metal and fiber removal, accumulation, screening, and storage of micronized powders. During the cryogenic grinding process a dusting agent is used to prevent the powder particles sticking to themselves. An example of such a dusting agent is talc. The present inventors found that by using an amount of 0.1-4.0 wt. %, preferably an amount of 0.3-1.5 wt. %, of fluffy synthetic precipitated amorphous silica (for example Hisil 255C-D), based on the total weight of the micronized powders, instead of talc, that the sieve yield of the grinding fraction 0-187 microns increased from around 8% to around 40%. It was also observed that a higher amount of tyre fibres (mixture of polyamide, polyester and rayon) could be removed from the MRP as the silica apparently reduced the forces of attraction between the rubber and the fibre. The present inventors assume that there might be some interaction between the silica and the silane. Such interaction may contribute to the attractive effects observed when using silane as the activation chemical.

(30) For the purpose of promoting an understanding of the principles of the present invention, reference will now be made to the embodiments illustrated in the tables. It will, nevertheless, be understood that no limitation of the scope of the disclosure is thereby intended; any alterations and further modifications of the described or illustrated embodiments, and any further applications of the principles of the disclosure as illustrated therein are contemplated as would normally occur to one skilled in the art to which the invention relates.

(31) The term functionalized or activated generally refers to functionalized or devulcanized material made from micronized rubber powders, as described herein above. The terms functionalized and activated are terms within the context having the same meaning. Such meaning is the ability to create crosslinks during vulcanization.

(32) The term subjected to shear generally refers to a process of feeding the rubber formulation into the nip between first and second counter-rotating rolls, wherein the first roll is rotating at a different speed than the second roll.

(33) The practice of the present invention can be further understood by reference to the following examples, which are provided by way of illustration only are not intended to be limiting.

EXAMPLES

(34) Several test examples (see Table 1 and 2) were prepared out to investigate the performance of the rubber composition.

(35) The test examples were compared with a so-called test recipe. The composition of the test recipe (according to ASTM D3191, ASTM D3191 excludes MRP) is shown in Table 1.

(36) TABLE-US-00001 TABLE 1 Composition of test recipe PPHR MATERIAL WEIGHT UNIT % 100 SBR 1500 29.82 grams 54.22 3 Zinc oxide 0.89 grams 1.63 1 Stearic acid 0.30 grams 0.54 50 N550 carbon black 14.91 grams 27.11 27.67 MRP sample 8.25 grams 15.00 1.75 Sulphur 0.52 grams 0.95 1 TBBS 0.30 grams 0.54 184.4 Total: 55.00 grams 100 Batch weight: 55

(37) The reference MRP sample is Cryofine 80 (Kargro) mesh, i.e. a cryogenically ground Micronized Rubber Powder produced exclusively from pre-selected end of life whole truck tyres, compliant with ASTM D5603 Class 80 1*.

(38) Samples #1-#43 were prepared by mixing the components mentioned in Table 1 together with specific components. The rubber composition thus obtained was tested for several parameters, such as Mooney viscosity, Rheology Scorch time, ts2, Rheology T90, Rheology Delta S, Tangent Delta, Tensile Strength, Payne Effect,

(39) M100M300, Ultimate Elongation, Tear Strength, and Abrasion Loss. The results of these tests are shown in Table 2. On basis of these performance parameters an average improvement rate was calculated (%). An average improvement rate >40% is identified as acceptable.

(40) In Table 2 component Silane Si69 is Bis(triethoxysilylpropyl)tetrasulfide, Vestenamer 8012 is a trans-polyoctenamer, Alpha wax is polyethylene wax, Trigonox 29 and Luperox 231 are 1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

(41) From Table 2 one will see that sample #7 (6% Silane (Si69)) has an average improvement rate of 65.7%. For sample #43 an even higher average improvement rate is obtained, i.e. a value of 79.1%. A comparison between sample #7 and sample #42 shows that the combination of both silane and NR latex has resulted in a high average improvement rate.

(42) TABLE-US-00002 TABLE 2 Rheology MRP Mooney Scorch Rheology Rheology Tangent Sample Description Content Viscosity time, ts2 T90 Delta S Delta Ref Reference compound ASTM D3191 0 85% 120% 120% 117% 90% (target values) Ref Reference compound ASTM D3191 15% 100% 100% 100% 100% 100% (normalised values) untreated MRP 1 0.13% Chemlok 8212 + 4.6% water 15% 99% 101% 102% 104% 100% as carrier 2 0.12% Chemlok 8212 bonding agent 15% 99% 102% 103% 104% 98% 3 0.36% Chemlok 8212 bonding agent 15% 97% 102% 103% 105% 99% 4 0.6% Chemlok 8212 bonding agent 15% 96% 101% 103% 106% 97% 5 2% Silane (Si69) 15% 96% 100% 104% 107% 96% 6 4% Silane (Si69) 15% 95% 98% 100% 110% 97% 7 6% Silane (Si69) 15% 85% 112% 115% 112% 94% 8 2.4% NR latex (dry) 15% 94% 103% 106% 100% 99% 9 2.4% NR latex plus low amount of 15% 94% 101% 103% 107% 97% curative blend 10 7.9% NR latex (dry) 15% 88% 106% 106% 98% 99% 11 8.2% NR latex (dry) plus high 15% 90% 99% 104% 115% 89% amount of curative blend 12 8% NR latex (dry) plus 1% organic 15% 88% 108% 112% 116% 92% peroxide curative 13 0.6% Megum W9500 bonding agent 15% 95% 101% 102% 108% 97% 14 1% SBR latex R4224 (dry) 15% 96% 105% 108% 103% 98% 15 3.1% SBR latex R4220 (dry) plus 15% 94% 101% 103% 107% 97% curative blend 16 3% Vestenamer granules plus high 15% 89% 104% 103% 115% 95% amount curatives 17 3% Vestenamer powder <500 m 15% 93% 104% 102% 116% 97% plus high amount curatives 19 3% Vestenamer powder <125 m 15% 86% 104% 102% 115% 95% plus high amount curatives 20 High amount curatives (whithout 15% 99% 98% 97% 100% 98% Vestenamer) 21 3% % Vestenamer cryogenic 15% 84% 106% 109% 106% 94% powder <400 m pre-mix plus low amount curatives 22 3% % Vestenamer cryogenic 15% 83% 104% 103% 115% 95% powder <400 m pre-mix plus high amount curatives 23 1% organic peroxide Trigonox 29 15% 95% 101% 102% 104% 100% 24 2.3% NR latex (dry) plus 0.6% 15% 94% 101% 103% 115% 97% peroxide Trigonox 29 25 10% Alpha wax SX70 plus 1% 15% 73% 100% 114% 106% 99% predispersed sulphur (active content) 26 10% Alpha Carisma 62 SX70 wax 15% 71% 99% 112% 104% 101% plus 1% predispersed sulphur (active content) 27 10% Alpha Carisma Glossy wax 15% 73% 102% 111% 104% 103% plus 1% predispersed sulphur (active content) 28 10% Alpha SX 5928 wax plus 1% 15% 69% 98% 108% 106% 101% predispersed sulphur (active content) 29 2.5% NR latex premix with 15% 94% 99% 104% 112% 95% colloidal sulphur colloidal ZnO 30 1.6% colloidal sulphur (active 15% 96% 98% 95% 111% 97% content) 31 1.8% peroxide Luperox 231M90E 15% 98% 100% 100% 107% 96% (active content) 32 1% Luperox 231M50 E ( active 15% 98% 101% 101% 104% 98% content) 33 1% Trinseo SBR latex K1 15% 91% 105% 107% 103% 98% 34 1% Trinseo SBR latex K2 15% 99% 97% 97% 96% 103% 35 1% Trinseo SBR latex K3 15% 96% 102% 105% 100% 101% 36 1% Trinseo SBR latex K4 15% 94% 105% 107% 103% 98% 37 1% Trinseo SBR latex K5 15% 98% 99% 97% 105% 98% 38 2.8% Silane (Si69) + 2.8% BDGA + 15% 82% 112% 116% 112% 93% 0.6% SBR latex (dry) + 8.3% Alpha Carisma Glossy 39 9% Silane (Si69) 15% 96% 97% 99% 117% 90% 40 4.5% Silane (Si69) + 4.5% BDGA 15% 84% 96% 108% 110% 98% 41 0.6% Silane (Si69) + 2% NR latex 15% 90% 101% 102% 108% 97% (dry) 42 0.6% Trigonox 29-C50 (active 15% 92% 100% 103% 115% 97% content) + 2% NR latex (dry) 43 5.9% Silane (Si69) plus 6% NR latex 15% 84% 122% 116% 112% 94% (dry) Improve- ment Tensile Payne Ulitmate Tear Abrasion Rating, Extrude to Sample Strength Effect M100 M300 Elongation Strength Loss Ave, % solid Ref 125% 70% 117% 121% 110% 131% 62% 100.0 N/A Ref 100% 100% 100% 100% 100% 100% 100% 0.0 no 1 102% 98% 101% 101% 99% 102% 95% 7.9 no 2 104% 94% 103% 106% 101% 101% 94% 15.4 no 3 107% 92% 104% 108% 101% 106% 92% 22.0 no 4 106% 90% 105% 107% 100% 109% 91% 24.8 no 5 105% 87% 106% 107% 103% 108% 92% 27.2 no 6 104% 84% 105% 108% 98% 115% 89% 28.7 no 7 111% 74% 109% 111% 110% 121% 81% 65.7 no 8 102% 99% 99% 98% 105% 103% 98% 10.2 yes 9 105% 83% 104% 106% 103% 108% 94% 27.2 yes 10 101% 99% 102% 103% 107% 120% 82% 29.5 yes 11 117% 75% 109% 110% 101% 121% 72% 59.1 yes 12 115% 76% 112% 110% 88% 125% 74% 61.4 yes 13 106% 90% 105% 107% 102% 109% 89% 27.2 no 14 105% 95% 104% 104% 105% 104% 100% 19.3 no 15 105% 84% 104% 105% 105% 108% 94% 27.2 no 16 102% 75% 115% 114% 95% 117% 69% 53.9 yes 17 96% 79% 113% 112% 93% 114% 72% 42.9 yes 19 99% 75% 115% 113% 95% 117% 71% 52.4 yes 20 97% 106% 105% 104% 92% 103% 98% 2.0 no 21 105% 80% 106% 108% 101% 103% 93% 36.6 yes 22 102% 95% 115% 114% 102% 118% 69% 51.6 yes 23 102% 98% 101% 101% 100% 102% 95% 9.8 no 24 107% 83% 104% 106% 103% 112% 70% 42.1 yes 25 103% 91% 106% 107% 110% 107% 87% 40.6 no 26 101% 96% 103% 104% 115% 102% 90% 32.3 no 27 98% 101% 99% 101% 111% 95% 106% 15.0 no 28 101% 96% 106% 108% 107% 109% 100% 30.3 no 29 111% 78% 110% 112% 101% 118% 71% 50.8 yes 30 113% 89% 109% 111% 102% 108% 60% 41.3 no 31 104% 87% 111% 110% 97% 117% 69% 37.8 no 32 100% 93% 105% 106% 106% 123% 74% 32.7 no 33 104% 95% 104% 103% 105% 107% 98% 22.0 no 34 94% 106% 95% 97% 92% 103% 105% 16.5 no 35 98% 102% 100% 99% 98% 103% 104% 0.8 no 36 103% 95% 104% 103% 111% 107% 93% 24.8 no 37 94% 106% 95% 97% 92% 103% 71% 3.5 no 38 112% 75% 115% 117% 90% 110% 65% 66.5 no 39 106% 69% 118% 125% 94% 115% 60% 61.4 no 40 109% 86% 104% 107% 112% 108% 89% 38.2 no 41 106% 90% 105% 107% 102% 109% 81% 32.3 yes 42 107% 83% 104% 106% 107% 112% 75% 42.1 yes 43 120% 74% 109% 111% 110% 121% 68% 79.1 yes

(43) TABLE-US-00003 TABLE 3 Composition of test recipe PPHR MATERIAL WEIGHT UNIT % 100 Natural Rubber 29.04 grams 52.8 TSR-10 5 Zinc oxide 1.45 grams 2.6 3 Stearic acid 0.87 grams 1.6 50 N375 carbon black 14.51 grams 26.4 28.4 MRP sample 8.24 grams 15.0 2.5 Sulphur 0.72 grams 1.3 0.6 TBBS 0.17 grams 0.3 189.5 Total: 55.00 grams 100 Batch weight: 55.00

(44) Several additional test examples (see Table 3 and 4) were prepared out to investigate the performance of the rubber composition.

(45) The test examples were compared with a so-called test recipe. The composition of the test recipe (according to ASTM D3191, ASTM D3191 excludes MRP) is shown in Table 3.

(46) The reference MRP sample is Cryofine 80 (Kargro) mesh, i.e. a cryogenically ground Micronized Rubber Powder produced exclusively from pre-selected end of life whole truck tyres, compliant with ASTM D5603 Class 80 1*.

(47) Samples #1-#11 (see Table 4) were prepared by mixing the components mentioned in Table 3 together with specific components. The rubber composition thus obtained was tested for several parameters, such as Mooney viscosity, Rheology Scorch time, ts2, Rheology T90, Rheology Delta 5, Tangent Delta, Tensile Strength, Payne Effect, M100, M300, Ultimate Elongation, Tear Strength, and Abrasion Loss.

(48) The results of these tests are shown in Table 4. On basis of these performance parameters an average improvement rate was calculated (%).

(49) TABLE-US-00004 TABLE 4 Rheology MRP Mooney Scorch Delta Tangent Tensile Sample Description Content Viscosity time, ts2 T90 S Delta Strength Ref Reference Compound 0 85% 120% 120% 117% 90% 125% ASTM D3191 (target values) Ref Reference Compound 15% 100% 100% 100% 100% 100% 100% MRP ASTM D3191 (normalized values) untreated MRP 1 0.5% Ultrasil VN3 + 2% 15% 92% 100% 104% 103% 98% 106% Si69 2 0.5% Ultrasil VN3 + 3% 15% 91% 108% 111% 104% 95% 117% Si69 3 0.5% Ultrasil VN3 + 4% 15% 91% 110% 112% 111% 95% 116% Si69 4 0.5% Ultrasil VN3 + 5% 16% 89% 112% 115% 110% 94% 118% Si69 5 0.5% Ultrasil VN3 + 6% 15% 86% 112% 115% 116% 92% 111% Si69 6 0.5% Ultrasil VN3 + 1% 15% 92% 107% 106% 105% 93% 106% Coupsil 8113 + 2% Si69 7 0.5% Ultrasil VN3 + 1% 15% 90% 109% 110% 105% 94% 117% Coupsil 8113 + 3% Si69 8 0.5% Ultrasil VN2 + 1% 15% 90% 111% 114% 111% 94% 117% Coupsil 8113 + 4% Si69 9 0.5% Ultrasil VN3 + 1% 15% 89% 112% 116% 112% 94% 120% Coupsil 8113 + 5% Si69 10 0.5% Ultrasil VN3 + 1% 15% 88% 114% 116% 112% 94% 120% Coupsil 8113 + 6% Si69 11 1% Coupsil 8113 + 5% 15% 87% 113% 116% 114% 92% 121% Si69 Improvement Payne Ultimate Tear Abrasion Rating Ave, Sample Effect M100 M300 Elongation Strength Loss %* Ref 70% 117% 121% 130% 131% 62% 100.0 Ref MRP 100% 100% 100% 100% 100% 100% 0.0 1 88% 106% 103% 108% 100% 97% 19.7 2 79% 111% 107% 110% 108% 90% 44.2 3 76% 110% 108% 114% 120% 88% 55.1 4 74% 111% 108% 119% 118% 82% 62.8 5 74% 113% 118% 110% 116% 81% 65.0 6 83% 106% 107% 122% 104% 95% 36.5 7 76% 109% 113% 126% 108% 89% 54.0 8 75% 113% 118% 124% 109% 81% 64.6 9 74% 113% 120% 123% 117% 80% 71.5 10 74% 115% 122% 112% 117% 75% 71.9 11 74% 114% 120% 120% 126% 75% 78.8 *Improvment rating = average retention of reference compound properties containing no MRP compared with the reference compound containing untreated MRP

(50) In Table 4 Ultrasil VN3 is SiO.sub.2, synthetically produced amorphous silicon dioxide (Evonik), Coupsil 8113 is precipitated silica, surface-modified with organosilane Si 69 (Evonik) and Silane (Si69) is a polyfunctional (polysulphide) silane (Evonik).

(51) From Table 4 one will see that samples #1-5 (containing 0.5% Ultrasil VN3 and between 2-6% Silane (Si69)) show an improvement rating of between 19.7% and 65%. Samples #6-10 (containing 0.5% Ultrasil VN3, 1% of Coupsil 8113 and between 2-6% Silane (Si69)) show an improvement rating of between 36.5% and 71.9%. Sample #11 (containing 1% Coupsil 8113 and 5% Silane (Si69)) shows the best improvement rating of 78.8%.

(52) The present inventors found that Ultrasil VN3 is a very effective dusting agent for deagglomerating the rubber particles after the cryogenic grinding process. Deagglomeration needs to take place in order to effectively sieve the fraction having the desired particle size distribution (D95<180 microns) and to screen out oversize particles for further processing. Clearly, when powder particles are stuck together they cannot be classified according to their size. The process of deagglomeration is also important to maximize the surface area of the powder to ensure that the activation chemicals have the possibility to coat the maximum amount of the powder's surface area. Ultrasil VN3being highly receptive to hydrophobation and condensation reaction with silane Si69also plays a role in the activation step.

(53) The present inventors found that Coupsil 8113 has a similar effectiveness as Ultrasil VN3 as a dusting/deagglomeration agent. However, Coupsil 8113 plays a more significant role than Ultrasil VN3 as an activation chemical because it is coated with about 11% of Si69. Therefore, for example, Coupsil 8113 can fully replace Ultrasil VN3 as a dusting agent, meaning that VN3 would not need to be used at all.

(54) The present inventors found that a combination of Coupsil 8113 (with a concentration of 1 wt. %) and Si69 at 4 wt. % concentration provides good results. Si69 also works well at 6 wt. % concentration without using any Coupsil 8113 but with using the dusting agent (0.25-0.5 wt. % of Ultrasil VN3) but such option is less costs attractive than adding 1 wt. % Coupsil 8113+4 wt. % Si69.