Abstract:
The invention is directed to bis-(2-ethylamino-4-diethylamino-s-triazine-6-yl)-tetrasulfide and a process for its production from the corresponding mercaptotriazine. The compound of the invention is employed in vulcanizable mixtures as a cross-linker or as vulcanization accelerator.

Description:
This is a division of application Ser. No. 693,343, filed Jan. 22, 1985, now U.S. Pat. No. 4,621,121. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention is directed to bis-(2-ethylamino-4-diethylamino-s-triazine-6-yl) tetrasulfide (V 480), a process for its production, its use, and vulcanizable mixtures containing it. The corresponding disulfide is known from German Pat. No. 1,669,954 and the related Westlinning U.S. Pat. No. 3,801,537. The entire disclosure of Westlinning is hereby incorporated by reference and relied upon. The disulfide can be produced for example from the corresponding mercaptotriazine by oxidation with iodine or hydrogen peroxide. The compound thus obtained is employed as a vulcanization accelerator in rubber mixtures. 
     The problem to be solved by the invention is to find a compound which imparts better properties to vulcanizates and process for the production of the compound. 
     SUMMARY OF THE INVENTION 
     The subject matter of the invention is bis-(2-ethylamino-4-diethylamino-s-triazine-6-yl)-tetrasulfide (V 480) and a process for its production which comprises reacting an aqueous, alkaline solution of 2-ethylamino-4-diethylamino-6-mercaptotriazine in a 2-phase system with a solution of S 2  Cl 2  in an inert organic solvent at a temperature of &lt;+10° C., with the proviso that the solvent either does not dissolve the tetrasulfide or only slightly dissolves it. 
     Advantageously there is produced an alkaline solution of the mercaptotriazine which contains the alkali ions (e.g. sodium or potassium ions) and mercaptotriazine molecule in equimolar amounts. 
     However, preferably there is used an amount of alkali, especially sodium hydroxide which is about 5 to 10% higher. 
     This solution is mixed with an organic solvent, especially an aliphatic or cycloaliphatic hydrocarbon, especially benzene (gasoline), petroleum ether or cyclohexane, so that there is formed a 2-phase system and there is added a solution of S 2  Cl 2 , preferably in the solvent which also is premixed beforehand with the solvent for the mercaptotriazine. The temperature thereby should be below 10° C., preferably below 5° C. 
     S 2  Cl 2  is brought to reaction in equimolar amounts under vigorous stirring. Under the stated conditions the S 2  Cl 2  surprisingly acts exclusively in a codensing manner. 
     The molar ratio of S 2  Cl 2  to the mercaptotriazine is preferably from 1:1 to 1,01:1, especially from 1:1 to 1,1:1. 
     The product which precipitated was separated with the help of commonly known procedures and dried advantageously at 40-45° C. under a vacuum. 
     Other subject matter of the invention include the use of V 480 in vulcanizable rubber mixtures and the corresponding V 480 containing mixtures themselves. 
     In the use of the compound V 480 of the invention as cross-linker or vulcanization accelerator it clearly shows its superiority to the standard compounds as well as to the disulfide V 143. 
     There is an extensive palatte of accelerators available to the rubber processing industry, especially for sulfur vulcanization, of which the most important classes for all purpose rubbers are: benzthiazolylsulfenamide, bis-benzthiazolyldisulfide, and 2-mercaptobenzothiazole as well as their corresponding triazine derivatives . Besides there is a series of special compounds such as thiuramdisulfides and peroxides which also act as cross-linkers without further additives such as sulfur, but which also are frequently used in combination with sulfur. 
     Today, the quantitatively most significant in terms of practical use, especially for the vulcanization of all purpose rubbers are the benzthiazolylsulfenamides. 
     A substantial disadvantage of the just mentioned vulcanization accelerators, especially the sulfenamides, is their greatly increasing tendency to reversion of the vulcanizate with increasing vulcanization temperature, especially when using besides reversion susceptible types of rubber such as NR and polyisoprene. With increasing temperature the speed of reversion increases so greatly that on the one hand there is a drastic reduction of the cross-linking density at optimum vulcanization and on the other hand, there is a sharp decline of the optimum cross-linking density with a frequently unavoidable over vulcanization. This is of similar concern but applies to a lesser extent to the remaining accelerator of the class of benzothiazoles. 
     These disadvantages of the benzothiazole accelerators limit their usability with increasing vulcanization temperature and places limits in reference to the efforts of the processing industry to increase productivity by the use of higher vulcanization temperatures. 
     A further non-neglibible disadvantage today, especially of the sulfenamides, is that there is formed free amine during the vulcanization process, which, insofar as they are nitrosizable, can lead to the formation of toxic nitrosamines, which in the future can be expected to limit their areas of use through legislation. 
     Surprisingly V 480 proves to be a compound both in regard to its use as a cross-linker and also as a vulcanization accelerator in sulfur vulcanization, which imparts to the vulcanizates produced therewith even at high vulcanization temperatures extraordinarily high reversion resistance. Therefore, they are predestined for use with high temperature vulcanization and therewith make possible increases in productivity. 
     The use of V 480 includes known rubber mixtures according to the state of the art such as natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), isobutylene isoprene rubber (IIR), ethylene-propyleneterpolymer rubber (EPDM), nitrile rubber (NBR), halogen containing rubber (e.g. polychloroprene or chlorinated natural rubber) and especially natural rubber which is epoxidized up to 75% (ENR), as well as their mixtures. The presence of double bonds is essential. The use of V 480 has particular significance of the reversion susceptible isoprene and natural rubbers, as well as their blends with other rubbers, V 480 is employed in sulfur containing rubber mixtures in an amount of 0.3 to 15, preferably 0.3 to 5 parts by weight per 100 parts of rubber. 
     In sulfur-free rubber mixtures there is used in an amount of 0.3 to 10, preferably, 0.3 to 5 parts by weight of V 480 per 100 parts by weight of rubber. 
     The rubber mixtures also contain the customary reinforcing system, i.e. furnace blacks, channel blacks, flame blacks, thermal blacks, acetylene blacks, arc blacks, (K blacks etc. as well as synthetic fillers such as silicas, silicates, aluminum oxide hydrate, calcium carbonate, and natural fillers such as clays, siliceous chalks, chalks, talcs, etc, and their blends in an amount of 5 to 300 parts per 100  parts of rubber ZnO and stearic acid as vulcanization promoters in an amount of 2 to 5 parts, 
     customarily used antiagers, ozone protectants and fatigue protectants such as, e.g. IPPD, TMQ, as well as waxes as light protectants and their blends, 
     plastizers at pleasure such as e.g. aromatic, naphthenic, parrafinic, synthetic plasticizers, and their blends 
     optionally retarders such as e.g. N-cyclohexylthiophthalimide, (N-trichloromethylthiophenylsulfonyl)-benzene and their blends, 
     optionally silanes such as e.g. bis-(3-triethoxysilylpropyl)-tetrasulfide, gamma-chloropropyltriethoxysilane, gamma-mercaptopropyltrimethoxysilane, ##STR1## and their blends, in an amount of 0.1 to 20, preferably 1 to 10 parts per 100 parts of filler, 
     optionally sulfur in an amount of 0.5 to 4 parts per 100 parts of rubber, 
     optionally other customary accelerators customarily employed as secondary accelerators in the rubber industry, especially Vulkalent E, in an amount of 0.2 to 4 parts, preferably 0.6 to 1.8 parts based on 100 parts of rubber, optionally additional sulfur doners, optionally dyes and processing aids. 
     The area of use extends to rubber mixtures, as they are customarily used in making tires, to industrial articles, such as e.g. mixtures for conveyor belts, V-belts, molded articles, piles with or without insertions, rubber rolls, linings, spray profiles, freehand articles, films, shoe soles and uppers, cables, full gum tires, and their vulcanizates. 
     Unless otherwise indicated all parts and percentages are by weight. 
     The compositions can comprise, consist essentially of, or consist of the stated materials and the process can comprise, consist essentially of, or consist of the recited steps with such materials. 
     While V 480 can be used with advantage in high temperature vulcanization it also can be used with conventional lower temperature vulcanization. 
    
    
     DETAILED DESCRIPTION 
     Example 1 
     454 grams of 2-diethylamino-4-ethylamino-6-mercaptotriazine were dissolved in aqueous sodium hydroxide which had been produced from 84 grams of NaOH and 1.5 liters of water. 
     The solution was placed in a liter threeneck flask, then there was added 1.5 liters of light benzine (B.P. 80-110° C.) and the mixture cooled to 0° C. with vigorous stirring. 
     There was then run in within 20 minutes a solution of 137 grams of S 2  Cl 2  in 100 ml of benzine whereby care was taken that the temperature did not exceed +50° C. 
     The tetrasulfide immediately precipitated out. At the end of the reaction the mixture was stirred for a further 5 minutes, subsequently sucked off and washed. 
     The snow white of fine powder was dried in a vacuum/12 Torr at 40-45° C. Amount: 499.5 grams, corresponding to 97.1% of theory; M.P. 149-150° C. 
     Analysis: Bis-(2-Ethylamino-4-diethylamino-s-triazine-6-yl)-tetrasulfide, Mol-Wt. 516, C 18  H 32  N 10  S 4   
     
         ______________________________________      C    H         N      S______________________________________Calculated   41.9   6.2       27.1 24.8Found        41.8   6.5       26.8 24.8______________________________________ 
    
     Testing Standards 
     The physical tests were carried out at room temperature according to the following standard specification (DIN stands for German Industrial Standard): 
     
         ______________________________________Tensile strength, elongation at               DIN 53504  MPabreak and on 6 mm thickrings modulusResistance to tear  DIN 53507  N/mmpropagationImpact elasticity   DIN 53512  %Shore A hardness    DIN 53505  --Mooney Test, ML 4   DIN 53524  --Goodrich Flexometer ASTM       °C.(Determination of heat               D 62362build-up ΔT)Firestone-Ball Rebound               AD 20245______________________________________ 
    
     In the use examples there are employed the following names and abbreviations whose meanings are given below: 
     
         ______________________________________RSS:             Ribbed Smoked Sheet            (natural rubber)Corax ® N 220:            Carbon Black, Surface            Area (BET) 120 m.sup.2 /g            (Degussa)Naftolen ZD:     Hydrocarbon PlasticizerIngralen 450:    Aromatic hydrocarbon            plasticizerIngroplast NS:   Naphthenic hydrocarbon            plasticizerVulkanox 4010 NA:            N--Isopropyl-N&#39;--phenyl-            p-phenylene-diamineVulkanox HS:     Poly-2,2,4-trimethyl-1,            2-dihydroquinolineMesamoll:        Alkylsulfonic acid ester            of phenyl and cresolProtektor G35:   Wax protector against            ozoneVukacit MOZ:     N--Morpholine-2-benzo-            thiazolsulphenamideVulcacit Mercapto:            2-MercaptobenzothiazoleVulcacit Thiuram:            Tetramethyl-thiurammono-            sulfideVulcazit CZ:     N--Cyclohexyl-2-benzo-            thiazolesulphenamideVulcalent E:     (N--trichloromethylthio-            phenylsulfonyl)-benzenePVI:             N--Cyclohexylthiophthal-            imideUltrasil VN3:    Precipitated silica            (Degussa)Gran.:           GranulateV143:            Bis-(2-Ethylamino-4-di-            ethylamino-s-triazine-            6-yl)-disulfide______________________________________ 
    
     Example 2 
     Reversion Stability With V 480 As Cross-Linker (Carbon Black As Filler) 
     
         ______________________________________          1       2       3______________________________________RSS 1, Ml 4 = 67 100       100     100CORAX N 220      50        50      50ZnO RS           5         50      5Stearic acid     2         2       2Naftolen ZD      3         3       3Vulkanox 4010 NA 2.5       2.5     2.5Vulkanox HS      1.5       1.5     1.5Protektor G 35   1         1       1Vulkacit MOZ     1.43      --      --V 143            --        1.29    --PVI              --        0.4     --V 480            --        --      4Sulfur           1.5       1.5     -- ##STR2##170° C.   30.0      8.5     2.3______________________________________ 
    
     The example shows that reversion stability was obtained using V 480 without sulfur. As reference systems there were used in mixture 1 MOZ in a so-called semi-efficient dosing, which according to the state of the art has been evaluated as very good and in sample 2 there was used the already reversion stable accelerator V 143. 
     Example 3 
     Temperature Dependence Of The Reversion Behavior Using V480 (Carbon/Silica As Fillers) 
     
         ______________________________________          4       5       6______________________________________RSS 1, ML 4 = 67 100       100     100CORAX N 220      25        25      25Ultrasil VN 3 B Gran.            25        25      25ZnO RS           5         5       5Stearic acid     2         2       2Naftolen ZD      3         3       3Vulkanox 4010 NA 2.5       2.5     2.5Vulkanox HS      1.5       1.5     1.5Protektor G 35   1.5       1.5     1.5V 480            --        --      3Vulkacit MOZ     1.43      --      --V 143            --        1.29    --Sulfur           1.5       1.5     -- ##STR3##145° C.   22.4      11.3    0160° C.   38.8      20.9    0170° C.   47.4      30.3    1.9180° C.   52.6      38.7    4.6______________________________________ 
    
     Mixtures in which carbon black is partially replaced by silica are especially susceptible to reversion. Mixture 6 shows that V 480 used as a cross-linker, i.e., without sulfur, imparted to the vulcanizate even at the highest vulcanization temperatures the utmost resistance to reversion. 
     Example 4 
     Vulcanization Stability With Overheating At 170° C. Using V 480 
     
         ______________________________________        7       8         9______________________________________RSS 1, ML 4 = 67          100       100       100CORAX N 220    25        25        25Ultrasil Un 3 Gran.          25        25        25ZnO RS         5         50        5Stearic acid   2         2         2Naftolen ZD    3         3         3Vulkanox 4010 NA          2.5       2.5       2.5Vulkanox HS    1.5       1.5       1.5Protektor G 35 1         1         1Vulkacit MOZ   1.43      --        --V 143          --        1.29      --V 480          --        --        3Sulfur         1.5       1.5       -- ##STR4##170° C. 44.7      28.7      2.6Vulcanization time       *t.sub.95%at 170° C.        t.sub.95%+ 50&#39;Tensile Strength          17.2      16.0      19.3          12.5      11.2      19.7Modulus 300%   5.1       3.7       5.5          3.3       2.8       5.3Tear PropagationResistance     32        16        29          6         5         28Firestone-Ball Rebound          54.9      52.8      53.5          51.3      51.7      53.2______________________________________ *t.sub.95% means that 95% of the vulcanization agent had been reacted; t.sub.95%+ 50&#39; means that it was heated for a further 50 minutes. 
    
     This example shows that with increasing reversion with overheating, namely 50&#39;/170° C. a greater decrease occurs in the physical vulcanization data. This can be seen especially clearly with mixture 7 in the tensile strength and 300% Modulus as well as in the resistance to tear propagation while in contrast mixture 9 in overheating the physical data remained practically unchanged. 
     Here also V 480 was compared to a semi-EV-system, which according to the state of the art already had been distinguished as resistant to reversion. 
     Example 5 
     Reversion Stability Using V 480 As Accelerator At a Vulcanization Temperature Of 170° C. 
     
         ______________________________________             10    11______________________________________RSS 1, ML 4 = 67    100     100CORAX N 220         50      50ZnO RS              5       5Stearic acid        2       2Naftolen ZD         3       3Vulkanox 4010 NA    2.5     2.5Vulkanox HS         1.5     1.5Protektor G 35      1       1Vulkacit MOZ        --      1.43V 480               1.5Sulfur              0.8     1.5 ##STR5##           0.8     29.2Tensile Strength    22.6    24.3Modulus 300%        11.0    10.4Elongation at Break 480     530Firestone-Ball Rebound               46.5    45.9Shore A Hardness    62      62______________________________________ 
    
     Example 5 shows that the combination of 1.5 parts V 480 with 0.8 parts sulfur always remain completely resistant to conversion at 170° C. compared to the corresponding sulfenamide and that with this combination at t 95%  practically the same data level is established. 
     Example 6 
     Influence Of The Sulfur Dosing On The V 480 Accelerator (Vulcanization Temperature: 170° C.) 
     
         __________________________________________________________________________        12  13  14  15  16  17__________________________________________________________________________RSS 1, Ml 4 = 67        100 100 100 100 100 100CORAX N 220  50  50  50  50  50  50ZnO RS       5   5   5   5   5   5Stearic acid 2   2   2   2   2   2Naftolen ZD  3   3   3   3   3   3Vulkanox 4010 NA        2.5 2.5 2.5 2.5 2.5 2.5Vulkanox HS  1.5 1.5 1.5 1.5 1.5 1.5Protektor G 35        1   1   1   1   1   1Vulkacit MOZ 1.43            --  --  --  --  --V 143        --  1.29                --  --  --  --PVI          --  0.4 --  --  --  --V 480        --  --  1.5 1.5 1.5 1.5Sulfur       1.5 1.5 0.8 1   1.2 1.4 ##STR6##t.sub.10%    3.8 4.2 3.1 2.9 2.9 2.8t.sub.80 -t.sub. 20%Vulcanizate data at        11.5            12.1                11.4                    12.1                        12.5                            13.1t.sub.95% Modulus 300%Shore A Hardness        63  66  63  63  64  65__________________________________________________________________________ 
    
     Example 6 shows that an increase of sulfur content beyond 0.8 is possible and leads to increase in modulus without reversion increasing very greatly. Indeed the raising of the sulfur content results in a slight shortening of the scorch properties. This can be counterbalanced through the use of Vulkalent E (see Example 7). 
     Example 7 
     Effect Of Customary Retarders On The Prevulcanization Time And Reversion Employing V 480 
     
         ______________________________________        18    19        20      21______________________________________RSS 1, ML (1 + 4) = 67          100     100       100   100CORAX N 220    50      50        50    50ZnO RS         5       5         5     5Stearic acid   2       2         2     2Naftolen ZD    3       3         3     3Vulkanox 4010 NA          2.5     2.5       2.5   2.5Vulkanox HS    1.5     1.5       1.5   1.5Protektor G 35 1       1         1     1Vulkacit MOZ   1.43    --        --    --V 480          --      1.5       1.5   1.5Sulfur         1.5     0.8       0.8   0.8PVI            --      --        1.2   --Vulkalent E    --      --        --    1.2Scorch time 130° C. min          21.5    8.0       17.5  21.0(increase 2 scaledivisions)Scorch at 170° C.          3.8     2.8       3.8   4.1(t.sub.10%)Modulus 300%   10.6    11.0      8.8   13.7______________________________________ 
    
     Example 8 
     Prolongation Of Scorch And Increase In Modulus Of V 480/Vucalent E--Combination 
     
         ______________________________________     22    23      24       25    26______________________________________RSS 1, Ml 4 = 67       100     100     100    100   100CORAX N 220 50      50      50     50    50ZnO RS      5       5       5      5     5Stearic acid       2       2       2      2     2Naftolen ZD 3       3       3      3     3Vulkanox 4010 NA       2.5     2.5     2.5    2.5   2.5Vulkanox HS 1.5     1.5     1.5    1.5   1.5Protektor G 35       1       1       1      1     1Vulkacit MOZ       1.43    --      --     --    --V 480       --      1.5     1.5    1.5   1.5Vulkalent E --      --      0.4    0.8   1.2Sulfur      1.5     0.8     0.8    0.8   0.8Scorch time 130° C.,       21.5    8.0     12.5   16.7  21.0Min. (increase 2scale divisions)Scorch time 170° C.       3.8     2.8     3.1    3.7   4.1(t.sub.10%), min.Modulus 300%       10.6    11.0    11.8   12.7  13.7______________________________________ 
    
     Example 9 
     Prolongation Of The Prevulcanization Time By Vulkalent E With The V 480 Vulcanization 
     
         ______________________________________        27    28        29      30______________________________________RSS 1, ML (1 + 4) = 67          100     100       100   100CORAX N 220    25      25        25    25Ultrasil VN3 Gran.          25      25        25    25ZnO RS         5       5         5     5Stearic acid   2       2         2     2Naftolen ZD    3       3         3     3Vulkanox 4010 NA          2.5     2.5       2.5   2.5Vulkanox HS    1.5     1.5       1.5   1.5Protektor G 35 1       1         1     1Vulkacit MOZ   1.43    --        --    --PVI            --      --        1.2   --V 480          --      3         3     1.5Vulkalent E    --      --        --    1.2Sulfur         1.5     0.8       0.8   0.8Scorch time 130° C.,          29.5    16.1      28.5  30.0Min (increase 2scale divisions)Scorch time 170° C.          4.5     3.6       4.2   4.7Modulus 300%   5.3     6.4       6.4   8.6______________________________________ 
    
     Example 9 shows the effectiveness of the retarder Vulkalent E in the case of a blend of carbon black and silica. Using 1.5 parts V 480, 0.8 parts sulfur and 1.2 parts of Vulkalent E there were obtained MOZ prevulcanization times without further doing anything. The reversion properties of V 480 vulcanization also were not negatively influences by the inclusion of retarders, no more than were the physical data of the vulcanizate. 
     Example 10 
     V 480 As Accelerator In SBR 
     
         ______________________________________          31      32      33______________________________________SBR 1712         137.5     137.5   137.5CORAX N 339      60        60      60ZnO RS           3         3       3Stearic acid     2         2       2Protektor G 35   1         1       1Vulkanox 4010 NA 1.5       1.5     1.5Vulkacit D       0.5       0.5     --Vulkacit CZ      1.45      --      --V 480            --        1.5     1.5Sulfur           1.6       1.5     1.5 ##STR7##Tensile Strength 20        19.2    23.1Modulus 300%     10.1      11.4    10.9Elongation at Break            480       430     460Shore A Hardness 63        65      64______________________________________ 
    
     Example 10 shows that V 480 also exerts a positive influence on the resistance to reversion in otherwise already reversion resistant SBR mixtures. 
     Example 11 
     Resistance To Reversion Of SBR-Vulcanization With V 480 
     
         ______________________________________             33    34______________________________________SBR 1500            100     100CORAX N 220         50      50ZnO RS              5       5Stearic acid        2       2Naftolen ZD         3       3Vulkanox 4010 NA    2.5     2.5Vulkanox HS         1.5     1.5Protektor G 35      1       1Vulkacit CZ         1.5     --V 480               --      1Sulfur              1.8     1.8 ##STR8##           12.1    9.1Vulcanizate data at t.sub.95% :Tensile Strength    20.2    21.8Modulus 300%        10.6    11.1Elongation at Break 450     460Resistance to Tear  13      14PropagationShore A Hardness    63      64______________________________________ 
    
     This sample shows that V 480 still further improves the reversion properties of the otherwise already slightly reversion susceptible SBR 1500. 
     Example 12 
     V 480 In Perbuban (Nitrile Rubber) 
     
         ______________________________________Perbunan N 3307 NS  100     100CORAX N 220         50      50ZnO RS              5       5Stearic acid        1       1Ingralen 450        5       5Mesamoll            10      10Vulkacit CZ         1.3     --V 480               --      1.5Sulfur              1.8     1.8 ##STR9##           9.5     6.9Vulcanizate data:Tensile Strength    19.5    18.8Modulus 300%        9.2     11.3Elongation at Break 480     380Shore A Hardness    64      65______________________________________ 
    
     As the example shows the inclusion of V 480 in place of a sulfenamide imparts further advantages in regard to resistance to reversion. 
     Example 13 
     V 480 In EPDM 
     
         ______________________________________Buna AP 541         100     100CORAX N 220         50      50ZnO RS              5       5Stearic acid        1       1Ingraplast NS       10      10Vulkacit Thiuram    1       --Vulkacit Mercapto   0.5     --V 480               --      2.5Sulfur                      1 ##STR10##          3.3     0Vulcanizate Data:Tensile Strength    16.0    16.0Modulus 300%        14.4    14.0Elongation at Break 320     350Shore A Hardness    72      69______________________________________ 
    
     For EPDM also through the inclusion of V 480 there results at the same regulation of the vulcanizate data the possibility still for further increase of the resistance to reversion. 
     Example 14 
     Simultaneous Use Of V 480 And Si 69 
     
         ______________________________________RSS 1, ML 4 = 67    100     100CORAX N 220         50      50ZnO RS              5       5Stearic acid        2       2Naftolen ZD         3       3Vulkanox 4010 NA    2.5     2.5Vulkanox HS         1.5     1.5Protektor G 35      1       1Vulkacit MOZ        1.43    --V 480               --      1.5Si 69               --      1.5Sulfur              1.5     0.4 ##STR11##          29.7    0Vulcanizate data:Tensile Strength    25.1    22.0Modulus 300%        10.2    10.8Firestone-Ball Rebound               45.2    44.2Shore A Hardness    63      62Goodrich-Flexometer 159     136delta T Center °C.______________________________________ 
    
     If there is replaced a portion of the sulfur (0.8 parts) by sulfur donors as for example polysulfidic silane, there likewise result an extraordinary reversion resistance by the example above. Furthermore, there occurs an extraordinary lowering of the build up of heat. 
     Example 15 
     V 480 Cross-Linking Of Epoxidized Natural Rubber Using Carbon Black And Silica As Filler 
     
         ______________________________________             1     2______________________________________ENR 50              100     100CORAX N 330         25      25Ultrasil VN 3 Gran. 25      25ZnO RS              5       5Stearic acid        2       2Vulkanox HS         2       2V 480               --      3Vulkacit MOZ        2.4     --Vulkacit Thiuram    1.6     --Sulfur              0.3     0.3Tensile Strength    15.1    15.6Modulus 100% (MPa)  8.4     11.0Further Tear Propagation               8       8DIN 53 507 (N/mm)Shore A Hardness    82      89DIN 53 505 23° C.______________________________________ 
    
     Example 16 
     V 480 Cross-Linking Of Epoxidized Natural Rubber Using Carbon Black Files 
     
         ______________________________________            1     2______________________________________ENR                100     100CORAX N 220        50      50ZnO RS             5       5Stearic acid       2       2Vulkanox HS        2       2V 480              --      4Vulkacit MOZ       2.4     --Vulkacit Thiuram   1.6     --Sulfur             0.3     0.3Tensile Strength DIN              18.7    27.053 504 Ring 1 (MPa)Modulus 300% (MPa) 18.0    19.0Resistance to further              12      12propagation DIN 53 507(N/mm)Shore A Hardness   75      80DIN 53 505 23° C.______________________________________ 
    
     The entire disclosure of German priority application is hereby incorporated by reference.