Reinforcing additive

The present invention is directed to additives for silicate or silica filler containing rubber mixtures which additives favorably influence the production of the rubber mixtures and the properties of the vulcanizate in a surprising and decisive manner. These additives belong chemically to the group of organosilicon compounds containing sulfur in the molecule. The additives impart to the silica (or silicate) fillers improved reinforcing properties and increase the over-all cross-linking of the vulcanization; they are designated as reinforcing additives in the following description.
It is known that carbon blacks generally, and especially the especially developed types of carbon black, are not present merely as fillers in rubber vulcanizate but take part in a specific manner as reinforcing fillers (active fillers). The influence of carbon black on the reinforcement of the polymers and the determination of the rubber-filler-reciprocal effect are described for example in the magazine "Kautschuk und Gummi, Kunststoffe", No. 8, pages 470-474 (1966) and No. 1, pages 7-14 (1970).
The silica (or silicate) fillers, i.e., siliceous materials as, for example, highly dispersed silica, silicates or the like are known to be different in their activity from carbon blacks. This difference is recognized by two kinds of facts. First the reinforcing effect of silica or silicate fillers is different from that of carbon black because of their completely different type of surface. Secondly, the active silica influence the vulcanization process, especially if the vulcanization is effected by sulfur and accelerator additives. Previously there have been no sulfur vulcanizations in which the silica (or silicate) fillers did not reduce the cross-linking.
In recent years there have been attempts to improve the activity of silica (or silicate) fillers by admixing chemical substances to the starting mixture.
Thus it is known to use mercaptomethylalkoxysilane as an adhesive promoter between silicate materials such as glass, clay, asbestos and silica dioxide (silica) and organic resins such as butadiene-styrene copolymers, natural rubber, polyester resins, polystyrene and styrene-maleic anhydride-mixed polymers, whereby this silane is introduced on the substrate in any desired manner and bound with the resin, see German Offenlegungsschrift No. 2,038,715.
Furthermore, there are known organosiliconsulfide compounds having a sulfidic sulfur atom between the hydrocarbon radicals which are recommended for use as adhesive promoters or also as intermediate products for compounds which can be used as water repelling agents or oxidizing agents. The named organosilicon compounds, however, can also have sulfur containing end groups such as thiocyanato, xanthogenato, thioether, thionic acid ester groups or the like, see Lee, German Auslegeschrift 1,911,227.
The organo-organooxysilanes, for example, the 3-thiocyanatopropyl-trimethoxy- or triethoxysilane, which according to Belgian Patent No. 770,097 and Rocktaschel U.S. application No. 163,467 filed July 16, 1971 find outstanding use in cross-linkable or vulcanizable mixtures of organic polymers, inorganic materials and the corresponding cross-linking or vulcanization agents or systems have similar end groups. The silanes described in German Auslegeschrift No. 1,911,227, Belgian patent 770,097 and the Rocktaschel U.S. application possess only a silicon atom bound to a carbon atom or a further silicon atom bound thereto by an oxygen atom or an amino nitrogen atom.
Furthermore there are known gamma-mercaptopropyltrimethoxy and triethoxy silanes as well as beta-mercaptoethyltriethoxy silane and other sulfur free silanes, which after subsequent partial hydrolysis and coating on the surface of silica or silicate filler particles serve to facilitate the workability of rubber mixtures and improvement of the strength properties of reinforced rubber articles, Vanderbilt U.S. Pat. No. 3,350,345.
Besides there are known tire threads produced form a rubber mixture which contain a silica as a filler and a silane as coupling agent, see Belgian Patent No. 760,099. An exceedingly large number of silanes are included in the general formula in the Belgian patent, but from the introduction, the tables and examples there can only be found gamma-mercaptopropyltrimethoxysilane as the single coupling agent tried.
The present invention is drawn to a class of organosilanes containing sulfur in the molecule which are distinguished in several respects from the numerous known silanes in their outstanding advantages in use and especially in their suitability and reinforcing additives as is described and shown below. The new additives produce in siliceous fillers (i.e., silica and silicates) containing rubber mixtures and vulcanizates unforeseen, valuable and industrially outstanding properties, whereby the rubber mixtures contain at least one rubber, a cross-linking system (e.g., including sulfur), a sulfur containing organosilane, fillers and preferably further conventional rubber additives. The invention is characterized by the rubber mixture containing as a strengthening additive one or more organosilanes of the formula:
I Z -- alk -- S.sub.n -- alk -- Z
in which Z is: ##STR2## and in which R.sub.1 is an alkyl group of 1 to 4 carbon atoms or phenyl and R.sub.2 is an alkoxy group with 1 to 8, preferably 1 to 4, carbon atoms, a cycloalkoxy group with 5 to 8 carbon atoms or a straight or branched chain alkylmercapto group with 1 to 8 carbon atoms. All the R.sub.1 and R.sub.2 groups can be the same or different. Alk is a divalent hydrocarbon group with 1 to 18 carbon atoms. It can be straight or branched chain and can be a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group or a cyclic hydrocarbon group. Preferably alk has 1 to 6, most preferably 2 or 3 carbon atoms and n is a [whole] number of 2 to 6, as well as one or more siliceous fillers (i.e. silica or a silicate), in a given case in admixture with carbon black. Preferably n is 2 to 4, more preferably 3 to 4.
Preferably the rubber mixtures contain at least one organosilane, especially one or two, most preferably one, of formula I in which Z stands for the group ##STR3## in which group R.sub.2 is an alkyl group with 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms and alk is a divalent straight chain saturated hydrocarbon radical (i.e., alkylene), having 1 to 6, preferably 2 or 3 carbon atoms. Besides the compounds named in the examples as preferred reinforcing additives, there can be used with advantage compounds of the formula ##STR4## where R.sub.2 is OCH.sub.3 ; -OCH.sub.2 CH.sub.3 ; OCH.sub.2 CH.sub.2 CH.sub.3 ; ##STR5## Other preferred silanes are those wherein in place of ##STR6## wherein R.sub.1 is alkyl (branched or unbranched with 1 to 4 carbon atoms), phenyl or cyclohexyl and R.sub.2 is as defined for formula II.
The new silanes used in the invention also have in the middle of the somewhat symmetrical molecule two or more connected sulfur atoms and two separated, to a certain degree, terminal standing silane groups. It must be accepted that this molecular structure causes the outstanding properties of the new vulcanization reinforcer.
The 3-mercaptopropyltrimethoxysilane already mentioned above in rubber mixtures which contain silica as a filler definitely increases the modulus values, tensile strength, abrasion resistance, rebound and shore hardness of the vulcanizate.
On the contrary, however, the scorch time and the Defo-elasticity of the unvulcanized mixtures are influenced unfavorably. The scorch times are shortened drastically. In the production of such mixtures even in the internal mixer frequently there occurs premature scorching which makes it impossible to further work the mixture.
The Defo-elasticity is sharply increased which means an increase of the elastic rubber portion in the crude mixture and makes more difficult the further processing, for example, by extrusion.
On the contrary, the rubber mixtures containing the new reinforcing additives employed in the present invention show definite industrial advantages in regard to the properties of the raw mixtures and the vulcanizates in comparison to those in the art. The raw mixtures now show especially a previously unknown degree of processing safety, a strongly reduced stiffness and only a slight increase of Defo-elasticity. All of these advantageous properties or effects for the first time open up the industrial use of such mixtures. The properties of the vulcanizates obtained are excellent and are comparable with the properties of correspondingly carbon black filled vulcanizates or even exceed these, as will be pointed out below. The mentioned improvement of the properties of the raw mixture and the vulcanizate for the first time opens field of use for silica fillers which previously were reserved for only carbon black as reinforcing filler.
The term "siliceous filler" is a broad term and refers to fillers which are rubber compatible or can be worked into rubber mixtures which fillers consist of silicates or silica, or contain silicates or silica and/or contain chemically bound silicates (or silica) in the widest sense, including mixtures of two or more siliceous fillers. Especially counted as siliceous fillers are:
Highly dispersed silica (silicon dioxide) having a specific surface area in the range of about 5 to 1000, preferably 20 to 400 m.sup.2 /g (determined with gaseous nitrogen according to the known BET procedure) and with primary particle sizes in the range of about 10 to 400 nm. (nanometer, 10.sup.-9 meters), which can be produced, for example, by precipitation from solutions of silicates, by hydrolysis and/or oxidative high temperature conversion. There can also be used flame hydrolysis of volatile silicon halides, e.g., silicon tetrachloride, or by electric arc processes. These silicas, in a given case, can also be present as mixed oxides or oxide mixtures with oxides of the metals aluminum (alumina), magnesium (magnesium oxide), calcium (calcium oxide), barium (barium oxide), zinc (zinc oxide), zirconium (e.g., zirconium dioxide), or titanium (e.g., titanium dioxide).
Synthetic silicates, for example, aluminum silicate or alkaline earth silicates such as magnesium, or calcium silicate with specific surface areas of about 20 to 400 m.sup.2 /g and primary particle sizes of about 10 to 400 nm.
Natural silicates, for example, kaolin, wollastonite, talc and asbestos as well as natural silicas, e.g., quartz or sand.
Glass fibers and glass fiber products such as mats, webs, strands, fabrics, non-woven fabrics and the like as well as microglass balls (microglass balloons).
The siliceous fillers mentioned can be added in amounts of about 10 or, in a given case, even less, up to about 250 parts by weight based on 100 parts by weight of rubber polymer.
As filler mixtures there can be used, for example, silicakaolin or silica-glass fibers-asbestos, as well as blends of siliceous reinforcing fillers with the mentioned rubber blacks, for example, silica-ISAF carbon black or silica-glass fiber cords HAF carbon black.
Typical examples of siliceous fillers usable in the invention, for example, are those produced by Degussa, such as silica or silicates under the tradenames Aerosil, Ultrasil, Silteg, Durosil, Extrusil, Calsil, etc.
Furthermore there can be mixed into the rubber mixtures various additives which are well known in the rubber industry and widely used.
There are several advantages if the additive of the invention is not added as such to the rubber mixture but first a mixture of at least one siliceous filler and at least one organosilane of formula I above is prepared and this is then or later incorporated in the rubber mixture or the remaining components of the mixture of the rubber mixture in the customary manner with the help of conventional mixing apparatus and homogeneously distributed therein.
In the production of the master batch, there is still a fluid, dry product if there is mixed into the siliceous filler an equal or even larger amounts by weight of liquid organosilane. Consequently, it is also possible to add only a portion of the entire fillers needed to produce the rubber mixture which as a master batch already contains the entire amount of necessary silane.
Examples of organosilanes within formula I which can be used in the invention are bis[trialkoxysilyl-alkyl-(1)]-polysulfides such as bis[2-trimethoxy-, -triethoxy-, -tri-(methyl-ethoxy)-, -tripropoxy-, -tributoxy and so forth up to -trioctyloxysilyl-ethyl]-polysulfides, namely the di-, tri-, tetra-, penta-, and hexasulfides, further the bis-[3-trimethoxy-, -triethoxy-, -tri-(methylethoxy)-, -tripropoxy-, -tributoxy- and so forth up to -trioctoxypropyl]- polysulfide, namely again the di-, tri-, tetra-, penta- and hexasulfide; furthermore the corresponding bis[3-trialkoxysilylisobutyl]- polysulfides, the corresponding bis[4-trialkoxysilyl-butyl]- polysulfides and so forth up to bis[6-trialkoxysilyl-hexyl]- polysulfides. Of those chosen, there are preferred relatively simply constructed organosilanes of formula I including bis-[3-trimethoxy-, -triethoxy-, and -tripropoxysilyl-propyl]- polysulfides namely the di-, tri- and tetrasulfides. These and the other organosilanes of formula I which can be added with good success can be made according to the process of Meyer-Simon application No. 277,043 filed on Aug. 1, 1973 which corresponds to German patent applications P 2141159.6; P 2141160.9 and P 2212239.9. The entire disclosure of Meyer-Simon (and the corresponding German applications) is hereby incorporated by reference. Typical examples of specific compounds within formula I which can be used in the invention include:
Examples of compounds within the invention include 3,3'-bis (trimethoxysilylpropyl) disulfide, 3,3'-bis (triethoxysilylpropyl) tetrasulfide, 3,3'-bis(trimethoxysilylpropyl) tetrasulfide, 2,2'-bis (triethoxysilylethyl) tetrasulfide, 3,3'-bis (trimethoxysilylpropyl) trisulfide, 3,3'-bis (triethoxysilylpropyl) trisulfide, 3,3'-bis (tributoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl) hexasulfide, 3,3'-bis(trioctoxysilylpropyl) tetrasulfide, 3,3'-bis(trihexoxysilylpropyl) disulfide, 3,3'-bis(tri-2"-ethylhexoxysilylpropyl) trisulfide, 3,3'-bis (triisooctoxysilylpropyl) tetrasulfide, 3,3'-bis(tri-t-butoxysilylpropyl) disulfide, 2,2'-bis(methoxy diethoxy silyl ethyl) tetrasulfide, 2,2'-bis (tripropoxysilylethyl) pentasulfide, 3,3'-bis (tricyclohexoxysilylpropyl) tetrasulfide, 3,3'-bis(tricyclopentoxysilylpropyl) trisulfide, 2,2'-bis(tri-2"-methylcyclohexoxysilylethyl) tetrasulfide, bis(trimethoxyxilylmethyl) tetrasulfide, 3,3'-bis (trimethyl-mercaptosilylpropyl) tetrasulfide, 2,2'-bis(triethylmercaptosilylethyl) disulfide, 2,2'-bis(tributylmercaptosilylethyl) trisulfide, 2,2'-bis(tri sec. butylmercaptosilylethyl) trisulfide, 3,3'-bis (trioctylmercaptosilylpropyl) tetrasulfide, 2,2'-bis (trihexylmercaptosilylethyl) hexasulfide, 3,3'-bis (ethyldipropylmercaptosilylpropyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl 3'-diethoxybutoxysilylpropyltetrasulfide, 2,2'-bis (dimethyl methoxysilylethyl) disulfide, 2,2'-bis(dimethyl sec.butoxysilylethyl) trisulfide, 3,3'-bis (methyl butylethoxysilylpropyl) tetrasulfide, 3,3'-bis(di-t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis (phenyl methyl methoxysilylethyl) trisulfide, 3,3'-bis (diphenyl isopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenyl cyclohexoxysilylpropyl) disulfide, 3,3'-bis(dimethyl ethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis(methyl dimethoxysilylethyl) trisulfide, 2,2'-bis(methyl ethoxypropoxysilylethyl) tetrasulfide, 3,3'-bis(diethyl methoxysilylpropyl) tetrasulfide, 3,3'-bis (ethyl di-sec. butoxysilylpropyl) disulfide, 3,3'-bis(propyl diethoxysilylpropyl) disulfide, 3,3'-bis(butyl dimethoxysilylpropyl) trisulfide, 3,3'-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenyl ethoxybutoxysilyl 3'-trimethoxysilylpropyl tetrasulfide, 4,4'-bis(trimethoxysilylbutyl) tetrasulfide, 6,6'-bis (triethoxysilylhexyl) tetrasulfide, 12,12'-bis(triisopropoxysilyl dodecyl)disulfide, 18,18'-bis(trimethoxysilyloctadecyl)tetrasulfide, 18,18'-bis(tripropoxysilyloctadecenyl) tetrasulfide, 4.4'-bis(trimethoxysilyl-buten-2-yl) tetrasulfide, 4,4'-bis (trimethoxysilylcyclohexylene) tetrasulfide, 5,5'-bis(dimethoxy methylsilylpentyl) trisulfide, 3,3'L -bis(trimethoxysilyl-2-methyl propyl) tetrasulfide, 3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.
The new silanes used in the invention can be added to the rubber mixture in amounts of 0.1 to 50 parts by weight, preferably within the limits of 0.5 to 25 parts by weight based on 100 parts by weight of rubber.
Unless otherwise indicated all parts and percentages are by weight.
For use the organosilanes described above can be directly added to the rubber mixture or to the constituents of this mixture. Thereby it is not necessary and not advantageous to hydrolyze the organosilane before the addition.
However, the described organosilicon compounds can also be added to a part of the fillers, especially on the basis of their easy dosability and handling, whereby the liquid organosilane is converted into a powdery product and thus be used. In a given case, however, it is also possible, although not of special advantage, to uniformly coat the organosilane on the surface of the filler particles and in this form to carry out the use. All three or only two of the described methods of use can also be combined.
The rubber mixtures can be produced with one or more, in a given case oil-extended, natural and/or synthetic rubbers. These include especially natural rubber, synthetic rubbers, preferably diene elastomus as for example polybutadiene, polyisoprene, e.g., cis-polyisoprene, butadiene- styrene copolymer, butadiene-acrylonitrile copolymer, polymerized 2-chlorobutadiene, also butyl rubber, halogenated butyl rubber such as chlorinated butyl rubber, brominated butyl rubber as well as other known diene rubbers as for example terpolymers of ethylene, propylene and for example non-conjugated dienes and also non-conjugated polyenes, e.g., ethylene-propylene-cyclooctadiene, ethylenepropylene-norbornadiene, ethylene-propylene dicyclo-pentadiene and ethylene-propylene-cyclododecatriene. Also there can be used trans-polypentenamer, carboxy or epoxy rubbers and the like known elastomers. The chemical derivatives of natural rubber and modified natural rubber can also be used in the invention.
There can be added, in a given case, to the rubber mixtures of the organic polymers, the cross-linking system, the siliceous fillers and the organosilane additive known reaction accelerators, as well as one or more compounds of the group of antiaging agents, heat stabilizers, light stabilizers, ozone stabilizers, processing aids, plasticizers, tackifier, propellants, dyestuffs, pigments, waxes, extenders such as for example sawdusts, organic acids as for example stearic acid, benzoic acid, or salicylic acid, additionally lead oxide or zinc oxide, activators such as for example triethanolamine, polyethylene glycol or hexanetriol-1,2,6, which are collectively known in the rubber industry. For the vulcanization the rubber mixture is generally mixed with cross-linking agents such as especially peroxides, e.g., benzoyl peroxide, sulfur or in special cases magnesium oxide, as well as in a given case vulcanization accelerators or mixtures of these.
The production of rubber mixtures as well as molding and vulcanization is carried out according to customary procedures in the rubber industry.
Industrial fields of use for the described rubber mixtures for example are:
Industrial rubber articles such as cable insulation, hoses, driving belts, V-belts, conveyor belts, roller coating, vehicle tire treads, especially PKW and LKW-tire treads, as well as tire carcasses and tire sidewalls, cross country tires, shoe sole materials, packing rings, damping elements and many others. The new rubber mixtures have also been tested for glass fiberadhesive mixtures and the like.
The filler Ultrasil VN2 is a precipitated active silica having a specific surface area (measured according to BET) of 130 m.sup.2 /g and an average primary particle size of 28 nm.
The Ultrasil VN3 is likewise a precipitated active silica but has a specific surface area of 210 m.sup.2 /g and an average primary particle size of 18 nm.
The rubber Buna CB10 is a polybutadiene rubber having a high cis-1,4- content.
Russ Corax 6LM is a ISAF-active carbon black wherein the large characters LM is an abbreviation for "Low Modulus".
Without limiting the invention the results are given in the following individual recipes for the new rubber mixtures with test results on the vulcanizates and evaluations or comparisons of these results. Therein many different concepts are repeated so that abbreviations can be used.
______________________________________Definitions of the Abbreviations UsedAbbreviation Designation Measured______________________________________DH Defo hardness grams (g)DE Defo elasticity --t.sub.5 Moooney-scorch time minutest.sub.35 Mooney-cure time minutesML 4 Mooney plasticity at 100.degree. C. standard rotor, testing time: 4 minutes --sp. gr. Specific gravity g/cm.sup.3VZ Vulcanization time minutesVT Vulcanization temperature .degree. C.ZF Tensile stength kp/cm.sup.2 (kgf/cm.sup.2)M(300, 200) Modulus kp/cm.sup.2 (kgf/cm.sup.2)BD Elongation at break %bl.D. Remaining elongation after break %E Rebound %EF Resistance to tear propagation kp/cm (kgf/cm)A Abrasion (also "DIN abrasion") mm.sup.3.DELTA.T Temperature increase (see Goodrich Flexometer) .degree. C______________________________________
Testing Standards
The physical tests were carried out at room temperature according to the following standard specifications:
______________________________________(DIN = German industrial standards)______________________________________Tensile strength, elongation at break and stretching value on 6 mm large rings DIN 53504Tear Propagation resistance DIN 53507Rebound DIN 53512Shore A hardness DIN 53505Specific gravity DIN 53550Mooney Test DIN 53524Goodrich Flexometer (Determination of the heat build-up, .DELTA.T ASTM D 623-62Abrasion DIN 53516______________________________________
The vulcanizates were always produced in a steam heated multiple die press at the stated vulcanization temperatures.
In the examples, and elsewhere unless otherwise indicated all amounts of materials are always given in parts by weight.

EXAMPLE 1
__________________________________________________________________________Recipe: Mixture 1 Mixture 2 Mixture 3__________________________________________________________________________Natural rubber (Ribbed Smoked Sheets I) 100 100 100Pentachlorthiophenyl-zinc salt (Renacit IV of Farbenfabriken BAYER) 0.25 0.25 0.25Finely divided precipi- tated silica (Ultrasil VN 3 of Degussa) 40 40 40Zinc oxide 3 3 3Stearic acid 2 2 23-mercaptopropyltrimethoxy- silane -- 2 --Bis-[3-trimethoxysilyl- propyl]-trisulfide -- -- 2Dibenzothiazyldisulfide 0.8 0.8 0.8Diphenylguanidine 2.25 2.25 2.25Sulfur 2.5 2.5 2.5__________________________________________________________________________
Mixing Procedure
Preliminary mixing was in a kneader at 80.degree. C. flow temperature
______________________________________Additive or Treatment Ended After______________________________________ Natural rubber 0 minutes 1/2 the amount of silica stearic acid 1 minute 1/2 the amount of silica zinc oxide and organosilane 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
This mixture was allowed to be stored for 24 hours. Then the final mixing took place in the kneader at 80.degree. C. flow temperature (Mixing Time 1.5 minutes).
__________________________________________________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2 Mixture 3__________________________________________________________________________DH/DE 675/20 precured 650/20 (scorched)t.sub.5 6.4 -- 5.0t.sub.35 7.5 -- 5.8ML 4 57 232 54 (increasing)sp.gr. 1.13 1.13 1.13Properties of the vulcanized MixtureVulcanization temperature: 150.degree. C.Mixture VZ ZF M 300 BD bl.D E SH EF A__________________________________________________________________________1 10 256 62 622 41 50 62 39 20 250 58 630 43 47 64 31 40 229 48 640 37 46 62 35 165 60 227 42 678 33 45 62 352 10 20 40 603 10 274 95 558 41 47 63 27 20 257 94 548 36 48 64 29 40 262 84 580 35 48 61 25 140 60 242 76 582 28 47 61 27__________________________________________________________________________
EXAMPLE 2
__________________________________________________________________________ Mixture Mixture MixtureRecipe: 1 2 3__________________________________________________________________________cis-1, 4-Polyisoprenerubber 100 100 100finely divided, precipitatedsilica (ULTRASIL VN 3 ofDEGUSSA) 50 50 50Plasticizer (naphthenichydrocarbons) 3 3 3Zinc oxide (active) 2 2 2Antioxidant (Mixture ofaralkylated Phenols) 1 1 1Mixture of equal parts of -finely divided precipitatedsilica and hexanetriol(Aktivator R of DEGUSSA) 4 4 4Benzoic acid 0.8 0.8 0.83-Mercaptopropyl-trimethoxysilane -- 1.5 --Bis-[3-triethoxysilyl-propyl]-tetrasulfide -- -- 1.5Dibenzothiazyldisulfide 0.8 0.8 0.8Diphenylguanidine 1.6 1.6 1.6Sulfur 2.5 2.5 2.5__________________________________________________________________________
Mixing Procedure
Premixing in a kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ cis-1.4-Polyisoprene rubber 0 minutes 1/2 amount of silica, stearic acid 1 minute 1/2 amount of silica, plasticizer, zinc oxide, organosilane 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
After standing for 24 hours final mixing was accomplished at 80.degree. C. flow temperature in a kneader. (Mixing time 1.5 minutes).
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2 Mixture 3______________________________________DH/DE 1500/6.0 scorched 1375/7.0t.sub.5 9.2 -- 6.5t.sub.35 11.6 -- 8.4ML 4 100 154 91 (increasing)sp. gr. 1.13 1.14 1.14Properties of the vulcanized MixtureVulcanization temperature: 134.degree. C.Mix-ture VZ ZF M 300 BD bl.D E SH EF A______________________________________1 10 136 21 707 17 33 48 20 20 198 27 742 24 36 59 30 196 30 215 31 733 30 36 61 28 40 220 34 723 34 38 61 232 10 20 30 403 10 199 47 632 23 40 63 40 20 242 63 640 31 42 68 44 158 30 266 79 628 36 43 71 41 40 272 87 620 41 44 72 43______________________________________
In examples 1 and 2 there were used a rubber mixture based on natural rubber or synthetic cis-1,4-polyisoprene which contained as the siliceous filler a precipitated finely divided silica (Ultrasil VN 3 of Degussa). As reinforcing additive for the rubber mixture there were employed bis-[3-trimethoxysilyl propyl]-trisulfide or bis-[3-triethoxysilyl propyl]-tetrasulfide and 3-mercaptopropyl trimethoxysilane was employed as a comparison material of the prior art. As is already shown by the properties of the unvulcanized mixture in producing mixtures in the internal mixer only the raw rubber mixtures of the invention are able to be worked up further while the comparison mixtures could not be further worked because of the premature scorching.
The polysulfide organosilanes of the invention only shorten the scorching time t.sub.5 and t.sub.35 a short time in the mixtures and do not negatively effect the Mooney plasticity (ML 4) as well as the ratio DH/DE, if the mixtures with the organosilane additives are compared with the standard or reference mixtures.
The vulcanization properties of the new rubber mixtures are, compared to the silane free standard mixtures, are somewhat better in their resistance and clearly superior in regards to 300 Modulus, whereby the reinforcing effect which is produced by the invention is proven by numerical data. The named important advantages were produced by means of the added organosilane.
Mixture 3 of example 2 additionally also shows extraordinarily high tear propagation resistance values (tear propagation resistance).
EXAMPLE 3
______________________________________ Mixture Mixture MixtureRecipe: 1 2 3______________________________________ Styrene-Butadiene-rubber (Buna Huls 1502) 100 100 100 Aluminumsilicate, precipi- tated (SILTEG AS 7 of DEGUSSA) 40 40 40 Zinc oxide (active) 3 3 3 Steric acid 1 1 1 Cumaron resin (B 1/2 85.degree. C.) 5 5 5 Mixture of equal parts of finely divided precipitated silica and hexanetriol (Activator R of DEGUSSA) 5 5 5 Antioxidant (Mixture of aralkylated phenols) 1 1 1 3-Mercaptopropyl- trimethoxysilane -- 1.5 -- Bis-[3-triethoxysilyl- propyl]-tetrasulfide -- -- 1.5 Benzothiazyl-2-cyclo- hexylsulfenamide 0.4 0.4 0.4 Diphenylguanidine 0.8 0.8 0.8 Sulfur 2.0 2.0 2.0______________________________________
Mixing Procedure
Premixing in a kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended after______________________________________ Polymer (SBR) 0 minutes 1/2 amount of aluminum silicate, stearic acid, antioxidant 1 minute 1/2 amount of aluminum silicate, plasticizer, zinc oxide, organosilane, remaining chemicals 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
Accelerator and sulfur were mixed in on the rolls (Mixing time 1.5 minutes).
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2 Mixture 3______________________________________t.sub.5 4.9 -- 3.1t.sub.35 5.9 -- 4.3ML 4 78 196 82 (increasing)sp. gr. 1.16 1.16 1.16Properties of vulcanized mixturesVulcanization temperature: 150.degree. C.Mix-ture VZ ZF M 300 BD bl.D E SH EF A______________________________________1 8 127 39 610 19 47 58 5 10 140 40 630 21 47 58 4 15 146 41 690 18 47 58 5 160 20 121 41 583 16 47 58 42 8 10 15 203 8 142 78 560 15 50 59 6 10 140 69 528 13 50 59 5 15 130 71 465 11 51 60 4 132 20 121 72 500 13 51 60 5______________________________________
EXAMPLE 4
______________________________________Recipe: Mixture 1 Mixture 2 Mixture 3______________________________________Styrene-Butadiene-rubber(Buna Huls 1502) 100 100 100Finely divided, precipitat-ed silica (ULTRASIL VN3 of DEGUSSA) 50 50 50Zinc oxide (active) 1 1 1Stearic acid 2 2 2Andioxidant (mixture ofaralkylated phenols) 1 1 1Polyethylene glycol,molecular wt. 4000(PEG 4000) 2 2 23-mercaptopropyl-trimethoxysilane -- 2 --Bis-[3-trimethoxysilyl-propyl]-disulfide -- -- 2Dibenzothiazyldisulfide 1 1 1Diphenylguanidine 2 2 2Sulfur 2 2 2______________________________________
Mixing Procedure
Premixing in a kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ Polymer (SBR) 0 minutes 1/2 amount of silica, stearic acid, antioxidant 1 minute 1/2 amount of silica, zinc oxide, organosilane, other 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2 Mixture 3______________________________________DH/DE 2250/19.5 scorched 2050/31.0t.sub.5 8.1 -- 7.8t.sub.35 10.0 -- 9.6ML 4 143 242 116 (increasing)sp. gr. 1.16 1.16 1.17Properties of the vulcanized mixturesVulcanization temperature: 150.degree. C.Mix-ture VZ ZF M 300 BD bl.D E SH EF A______________________________________1 5 170 40 660 40 33 71 17 10 174 42 640 34 33 72 14 15 178 41 625 31 33 71 13 126 20 196 42 647 30 33 71 142 5 10 15 203 5 208 63 592 33 32 70 17 10 222 77 548 29 32 71 13 15 222 85 523 24 32 70 14 89 20 216 85 513 21 32 71 13______________________________________
EXAMPLE 5
______________________________________Recipe: Mixture 1 Mixture 2 Mixture 3______________________________________Styrene-Butadiene-rubber(Buna Huls 1500) 100 100 100Colloidalkaolin 75 75 75Zinc oxide 4 4 4Stearic acid 2 2 23-mercaptopropyl-trimethoxysilane -- 2.5 --Bis-[3-triethoxysilyl-propyl]-tetrasulfide -- -- 2.5Dibenzothiazyldisulfide 1.2 1.2 1.2Diphenylguanidine 1.2 1.2 1.2Sulfur 2.75 2.75 2.75______________________________________
Mixing Procedure
Premixing in a kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ Rubber 0 minutes 1/2 amount of Kaolin, zinc oxide, organosilane 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
After 24 hours storage the mixing in the kneader at 80.degree. C. flow through temperature was completed (Mixing time 1.5 minutes).
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2 Mixture 3______________________________________DH/DE 1750/27 2550/32.5 1450/23.5t.sub.5 34.0 6.6 29.2t.sub.35 41.3 11.6 38.2ML 4 63 80 61sp. gr. 1.32 1.32 1.32Properties of the vulcanized mixturesVulcanization temperature: 150.degree. C.Mix-ture VZ ZF M 300 BD bl.D. E SH EF A______________________________________1 15 101 50 635 53 45 64 13 30 99 66 483 36 42 67 6 45 96 65 490 34 40 66 6 268 60 94 64 480 34 40 67 92 15 154 137 335 18 45 67 8 30 146 138 307 13 44 68 5 45 145 138 305 10 43 68 5 210 60 147 143 303 11 42 67 5 M 2003 15 125 77 440 22 42 66 8 30 125 101 287 14 41 69 5 45 125 102 262 10 40 69 5 223 60 129 104 293 14 39 69 4______________________________________
In examples 3 to 5 there were used rubber mixtures based on styrene-butadiene copolymers which contained as silicious fillers synthetic aluminum silicate or precipitated silica or a natural silicate (colloidal kaolin). As organosilane reinforcing additives there were employed bis[3-triethoxysilyl propyl]-tetrasulfide or bis-[3-trimethoxysilyl propyl]-disulfide; these were compared with the 3-mercaptopropyl trimethoxysilane of the prior art in otherwise identical mixtures.
According to examples 3 and 4 it was not possible to produce kneader mixtures with 3-mercaptopropyl trimethoxysilane without premature scorching while this presents no problem with the rubber mixtures containing the polysulfideorganosilanes of the invention.
In comparison with the respective standard mixtures without silane additive the vulcanization properties of the new rubber mixtures are clearly better. Tensile strength and modulus are increased, the remaining elongation after break was reduced and the DIN abrasion improved.
Example 5 shows that this effect occurs even in the addition of a relatively inactive silicate filler such as colloidal kaolin.
Example 5 also demonstrates with reference to the properties of the unvulcanized mixtures the clear advance of the present invention over the prior art compound 3-mercaptopropyl trimethoxysilane in that the prior art compound increases the values for DH/DE and ML 4 and it drastically shortens the scorch time t.sub.5. On the contrary in the new rubber mixtures the values DH/DE and ML 4 are changed in a positive direction while the Mooney-scorch time t.sub.5 is not substantially different from that of the comparison mixture without any silane additive.
The following examples 6 to 9 illustrate the fact that the new rubber mixtures also can be produced with equally good success based on butadiene -acrylonitrite copolymers, butyl rubber, polychloroprene rubber or ethylenepropylene-terpolymer.
EXAMPLE 6
______________________________________Recipe: Mixture 1 Mixture 2______________________________________Butadiene-acrylonitrile-rubber(Perbunan N 3310 of FarbenfabrikenBayer AG) 100 100Pyrogenic silica (Aerosil 130 Vof DEGUSSA) 40 40Zinc oxide 4 4Bis-[3-triethoxysilyl-propyl]tetrasulfide -- 1.5Dibenzothiazyldisulfide 1.5 1.5Diphenylguanidine 1.5 1.5Sulfur 2.75 2.75______________________________________
Mixing Procedure
Premixing in a kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ Butadiene-acrylonitrile-rubber 0 minutes 1/2 amount of silica, stearic acid 1 minute 1/2 amount of silica, zinc oxide, organosilane 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 4.5 minutes______________________________________
After 24 hours storage the mixing in the kneader at 80.degree. C. flow through temperature was completed (Mixing time 1.5).
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________DH/DE 2350/26 1950/31t.sub.5 10.6 7.8t.sub.35 13.4 9.8ML 4 132 105sp. gr. 1.21 1.21Properties of the vulcanized mixturesVulcanization temperature: 150.degree. C.Mix-ture VZ ZF M 200 BD bl.D. E SH EF A______________________________________1 60 182 99 303 3 18 76 12 80 178 110 285 3 17 77 10 107 100 161 106 265 2 17 76 12 120 158 109 262 1 17 79 132 60 200 179 218 1 16 78 7 80 210 189 215 1 16 78 9 58 100 226 187 215 1 16 77 9 120 228 204 225 2 16 78 8______________________________________
EXAMPLE 7
______________________________________Recipe: Mixture 1 Mixture 2______________________________________Butyl rubber 100 100Finely divided, precipitatedsilica (ULTRASIL VN 3 of Degussa) 50 50Zinc oxide 5 5Stearic acid 1 1Plasticizer (Petroleum oil) 5 5Bis-[3-triethoxysilyl-propyl]tetrasulfide -- 1.52-Mercaptobenzothiazole 1 1Tetramethylthiuramdisulfide 0.5 0.5Sulfur 1.5 1.5______________________________________
Mixing Procedure
Premixing in the kneader at 60.degree. C flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ Butyl rubber 0 minutes 1/2 amount of silica, stearic acid 2 minutes 1/2 amount of silica, zinc oxide, organosilane, plasticizer 4 minutes Ram lifted and swept down 6 minutes Batch dumped 7 minutes______________________________________
The final mixing took place on an open mill at 50.degree. C. roll temperature.
______________________________________Additive or Treatment Ended After______________________________________Batch charged 0 minutesCut in twice right and left 1 minuteAccelerator and sulfur 2 minutesCut in twice right and left 4 minutesMixture sheet pulled of 5 minutes______________________________________
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________DH/DE 4300/3 3200/5t.sub.5 1.2 2.9t.sub.35 40 17.6ML 4 135 112sp. gr. 1.15 1.15Properties of the vulcanized mixturesVulcanization temperature: 160.degree. C.Mix-ture VZ ZF M 300 BD bl.D. E SH EF A______________________________________1 10 85 19 893 100 12 64 15 20 103 23 850 100 13 67 16 40 117 27 818 100 13 68 23 60 116 28 795 96 13 70 25 270 80 112 28 778 93 13 70 262 10 108 27 805 97 11 63 17 20 133 34 773 78 11 64 22 40 145 40 738 68 12 67 23 60 148 43 708 64 12 69 28 227 80 151 45 693 63 12 69 27______________________________________
EXAMPLE 8
______________________________________Recipe: Mixture 1 Mixture 2______________________________________Polychlorobutadiene rubber 100 100(Baypren 210 of FarbenfabrikenBayer AG, Leverkusen)Di-o-tolylguanidine 0.5 0.5Magnesiumoxide 4 4Stearic acid 1 1Mixture of liquid and plasticparaffins (Vaseline) 1 1Phenyl-.beta.-naphthylamine (anti-oxidant) 2 2Finely divided, precipitatedsilica (ULTRASIL VN 2 of Degussa) 50 50Plasticizer(naphthenic hydrocarbons) 10 10Bis-[3-triethoxysilyl-propyl]tetrasulfide -- 1.52-mercaptoimidazoline 0.75 0.75Zinc oxide 5 5______________________________________
Mixing Procedure
Premixing in the kneader at 60.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________Polychlorobutadiene, guanidine derivate 0 minutesAntioxidant, magnesium oxideStearic acid, vaceline, 1/3 of the amount 1 minuteof the silica1/3 of the amount of the silica, 1/2 theamount of the plasticizer, organosilane 2.5 minutes1/3 the amount of the silica, 1/2 theamount of the plasticizerRam lifted and swept down 4 minutescoolingRemoval and 5 minutes in a waterbath 5 minutes______________________________________
After 24 hours storage there was mixed in the kneader at 60.degree. C flow temperature the 2-Merkaptoimidazoline and the zinc oxide and there was 5 minutes cooling in the waterbath.
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________DH/DEt.sub.5 6.2 5.5t.sub.35 10.8 10.1ML 4 91 84sp. gr. 1.42 1.42Properties of the vulcanized mixturesVulcanization temperature: 150.degree. C.Mix-ture VZ ZF M 300 BD bl.D. E SH EF A______________________________________1 10 156 47 810 28 34 57 37 20 167 52 790 18 33 61 31 30 171 53 742 17 33 62 23 161 40 171 53 735 15 33 62 192 10 196 75 673 17 37 60 29 20 208 105 555 10 36 63 14 30 214 113 532 10 35 64 11 105 40 216 119 513 10 35 65 14______________________________________
EXAMPLE 9
______________________________________Recipe: Mixture 1 Mixture 2______________________________________Terpolymer ethylene-propylene-rubber (Keltan 70 of DSM) 100 100Finely divided, precipitatedsilica (Extrusil of Degussa) 100 100Naphthenic hydrocarbon asplasticizer 50 50Titandioxide 10 10Zinc oxide 5 5Stearic acid 1 1Bis-[3-triethoxysilyl-propyl]tetrasulfide -- 5Tetramethylthiuramdisulfide 0.8 0.8Dimethyldiphenylthiuramidisulfide 1.5 1.5Telluriumdiethyldithiocarbamate 0.8 0.8Dipentamethylenethiuramtetrasulfide 0.8 0.8Sulfur 2.0 2.0______________________________________
Mixing Procedure
Premixing in the kneader at 80.degree. C. flow temperature.
______________________________________Additive or Treatment Ended After______________________________________ Ethylene-Propylene-Terpolymer 0 minutes 1/2 amount of the silica, stearic acid 1 minute 1/2 amount of the silica, zinc oxide organosilane, remaining chemicals 2.5 minutes Ram lifted and swept down 4 minutes Batch dumped 5 minutes______________________________________
After 24 hours storage the mixing was finished in the kneader at 80.degree. C. flow temperature (Mixing time 1.5 minutes).
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________DH/DE 550/17.5 400/19.5t.sub.5 8.5 19.2t.sub.35 16.4 50.4ML 4 50 40sp. gr. 1.16 1.16Properties of the vulcanized mixturesVaulcanization temperature: 160.degree. C.Mix-ture VZ ZF M 300 BD bl.D. E SH EF______________________________________1 10 67 23 825 43 43 53 7 20 62 29 627 25 42 57 3 30 55 32 550 21 42 59 22 10 77 42 725 26 41 54 8 20 91 74 392 7 43 60 3 30 98 98 300 5 44 63 2______________________________________
In example 6 there was used a rubber mixture formulated according to the invention based on a nitrile rubber which contained as the siliceous filler a pure silica produced by flame hydrolysis (Aerosil 130V of Degussa) and to which was added bis-[3-triethoxysilyl-propyl] -tetrasulfide as the organosilane reinforcing additive.
The Mooney viscosity of mixture 2 of Example 6 is clearly reduced in comparison to the standard mixture without organosilane addition. This signifies a reduced expenditure of energy and a lower cost in the further working of the raw mixture; the scorching time t.sub.5 is only shortened unsubstantially. The vulcanizate of Mixture 2 shows a significant improvement in regard to tensile strength, modulus and DIN-abrasion when it is compared with comparison mixture 1 without organosilane addition.
According to example 7 the rubber mixture of the invention was based on butyl rubber containing a precipitated silica (Ultrasil VN 3 of Degussa) as the siliceous filler and the bis-[3-triethoxy-silyl propyl]-tetrasulfide as the organosilane reinforcing additive.
This addition of organosilane did not lead to premature scorching of the already very sharply accelerated standard mixture, but instead surprisingly to an increase in the Mooney-scorch time t.sub.5. Tensile strength, modulus and remaining elongation of the vulcanizate were clearly better in comparison to the vulcanizate from the standard mixture.
Example 8 describes a rubber mixture based on a polychloroprene rubber with a precipitated silica (Ultrasil VN 3 of Degussa) as the siliceous filler and again using the bis-[3-triethoxysilyl propyl]-tetrasulfide as the organosilane reinforcer for cross-linking. The scorching behaviour of Mixture 2 is practically unchanged in comparison to the standard mixture, in regard to the Mooney viscosity Mixture 2 behaves somewhat more favourably. The properties of the vulcanizate of the rubber composition of the invention compared to those of the standard mixture are clearly superior. The tensile strength is more than 40 kp/cm.sup.2 (40 kgf/cm.sup.2) and the 300% modulus at the same time more than 60 kp/cm.sup.2 higher. The latter indicates an improvement of about 100% or more based on the Mixture 1 devoid of the organosilane.
Example 9 concerns a rubber mixture based on an ethylene-propylene nonconjugated diene-terpolymer with a further precipitated silica (Extrusil of Degussa) as the siliceous filler and the bis-[3-triethoxysilyl propyl]-tetrasulfide as the organosilane. Also in this case there is produced a surprising increase in the scorch time t.sub.5 ; ML 4 is reduced about 10 Mooney units, both in comparison to the standard mixture without organosilane. The properties of the vulcanizate from Mixture 2 formulated according to the invention clearly exceed those of Mixture 1 without silane in regard to tensile strength, modulus and remaining elongation after break.
EXAMPLE 10
______________________________________Passenger automobile - tire tread mixtureRecipe Mixture 1 Mixture 2______________________________________Oil extended styrene-butadiene rubber(Buna Huls 1712) 96.5 96.5cis-1,4-Polybutadiene(Buna CB 10) 30 30Finely divided precipitatedsilica (ULTRASIL VN 3 of Degussa) 75 70Bis-[3-triethoxysilyl-propyl]-tetrasulfide 5 --Mixture of equal parts ofprecipitated silica (ULTRASIL VN 3)and Bis-[3-triethoxysilyl-propyl]tetrasulfide -- 10Zinc oxide 4 4Stearic acid 1.2 1.2Plasticizer (naphthenichydrocarbons) 15 15Antioxidant, phenyl-.beta.-naphthyl-amine 1.5 1.5Antioxidant, N-Iso-propyl-N'-phenyl-p-phenylene-diamine 1.5 1.5Benzthiazolyl-2-cyclohexylsul-fenamide 1.2 1.2Diphenylguanidine 3.5 3.5Sulfur 1.6 1.6______________________________________
Mixing Procedure: "Up-side-down"
Premixing in the Kneader at 80.degree. C. flow temperature
______________________________________Additive or TreatmentStep 1 Ended After______________________________________ Fillers, chemicals, polymers 0 minutes Ram lifted and swept down 3 minutes Batch dumped 3.5 minutes Storage 24 hours______________________________________
Step 2
Final mixing in the kneader at 80.degree. C flow temperature. Accelerator and sulfur are mixed in in the kneader
Mixing time 1.5 minutes
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________t.sub.5 20.0 18.1t.sub.35 26.5 26.0ML 4 67 67sp. gr. 1.19 1.19Properties of the vulcanized mixturesVulcanization temperature: 160.degree. C.Mix-ture VZ ZF M 300 BD bl.D. E SH EF A______________________________________1 20 190 66 592 26 38 64 23 912 20 196 63 627 26 38 62 27 90______________________________________
EXAMPLE 11
______________________________________Tire tread mixtureRecipe: Mixture 1 Mixture 2______________________________________Natural rubber(Ribbed Smoked Sheets I) 100 100Pentachlorthiophenyl-zinc salt(Renacit IV of Farben-fabriken Bayer, Leverkusen) 0.25 0.25ISAF-LM Carbon black(CORAX 6 LM of Degussa) 60 --Mixture of 10 parts of bis[3-triethoxysilyl-propyl]-tetra-sulfide and 100 parts ofprecipitated silica (ULTRASILVN 3 of Degussa) -- 66Zinc oxide 5 5Stearic acid 2.5 2.5Antioxidant, phenyl-.alpha.-naphthylamine 1 1Antioxidant phenyl -.beta.-naphthylamine 1 1Antioxidant N-Isopropyl-N-phenyl-p-phenylendiamine 0.8 0.8Rubber-ccozerite (Protektor 3888of Luneburge Wachs-bleiche, GmbH) 0.8 0.8Plasticizer (naphthenichydrocarbon) 2 2Bis-[2-ethylamino-4-diethylamino-6-triazinyl]-disulfide 0.6 0.6Diphenylguanidine -- 2Sulfur 1.2 1.2______________________________________
Mixing Procedure: "Up-side-down"
Premixing in the kneader at 80.degree. C. flow temperature
______________________________________Additive or TreatmentStep 1: Ended After______________________________________ Fillers chemicals, polymer 0 minutes Ram lifted and swept down 3 minutes Batch dumped 3.5 minutes Storage time 24 hours______________________________________
Step 2:
Final mixing in the kneader at 80.degree. C. flow temperature. Accelerator and sulfur are mixed in in the kneader
Mixing time 1.5 minutes
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2______________________________________Mooney Scorch t.sub.5 25.4 19.9Mooney Cure t.sub.35 28.1 25.3Mooney viscosity ML 4 88 77sp. gr. 1.15 1.18Properties of the vulcanized mixturesVulcanization temperature: 145.degree. C.Mix- M Tture VZ ZF 300 BD E SH EF A (0.250")______________________________________1 60 249 139 490 36 68 31 102 872 60 257 119 547 41 76 42 104 64______________________________________
According to Example 10 a passenger automobile tire tread (PKW) recipe and according to Example 11 an earth mover tire tread recipe are disclosed and used. As reinforcing additive for both recipes there were used bis-[3-triethoxysilylpropyl]-tetrasulfide, for the PKW tire tread in the form of a mixture with silica in the ratio 1:1 and for the earth mover tire tread in the form of a mixture with finely divided silica in the ratio 1:10.
Example 10 shows that with the range of error of the rubber technique investigating methods used there was no difference between the application of the reinforcing additive in pure form and the application of the reinforcing additive in the form of a mixture with precipitated highly dispersed silica.
The properties of the unvulcanized and the vulcanized mixtures show one skilled in the art that by using the reinforcing additive of the invention there are imparted to a great extent to the silica reinforced PKW tire tread mixtures properties which correspond to the properties of corresponding carbon black mixture.
Also, for the first time, it is possible by use of the polysulfide functional organosilane reinforcing additive to produce silica reinforced PKW tire tread mixtures without change of the previously customary mixing and vulcanization processes in the rubber industry, which mixtures in all industrial applications have characteristics which are at least equal to corresponding carbon black reinforced mixtures.
In Example 11 the reinforcing additive of the invention in a silica reinforced Earth-Mover tire tread mixture is compared with a conventional carbon black reinforced Earth-Mover tire tread mixture.
In Example 11 it is proven that by using the additives of the invention there are imparted such properties to silica reinforced rubber mixture which in decisive points exceed those of carbon black reinforced mixtures; for example in regard to tear propagation resistance and the heat build up (Heat build-up Goodrich Flexometer Test).
In comparison to the standard Mixture 1 it is established that by use of the reinforcing additive of the invention the Mooney-scorch and Mooney cure time are somewhat shortened but they still remain in a range suitable for industrial practice. The raw mixture viscosity is 11 Mooney units lower in the composition of the invention in comparison to the standard mixture which is a altogether a desired effect since it leads f.i. to a reduction in the production costs for the tire manufacturer.
In the vulcanization properties which in general correspond to those of the standard mixture there are two properties in which the mixture of the invention stands out; the clearly increased resistance to tear propagation and the reduced heat build up. The resistance to tear propagation is increased 35% in comparison to the carbon black reinforced standard (or reference) mixture, the heat build up is lowered about 31%, from 87.degree. C. to 64.degree. C. In the evaluation of the absolute values of the Goodrich Flexometer test it should be observed that this was measured with a stroke of 0.250 inch, while ASTM prescribes a stroke of 0.175 inch. It is especially noteworthy that the DIN abrasions of the carbon black mixture and of the silica mixture are practically the same.
It was also again confirmed that by use of the organosilane reinforcing additive of the invention that for the first time it is possible to easily produce practical mixtures with only silica or siliceous filler and then to vulcanize which products in the sum of their properties are equal to corresponding carbon black filled mixtures and even exceed the carbon black mixtures in decisive characteristics.
The rubbers disclosed above are all curable, e.g., with sulfur or other curing (vulcanizing) agents.
The compositions of the invention can consist of or consist essentially of the siliceous filler and the organosilane or the composition can consist of or consist essentially of these components with the other materials mentioned.
EXAMPLE 12
______________________________________Passenger Car Tire Tread MixtureRecipe Mixture 1 Mixture 2______________________________________Oil extended styrene-butadiene rubber(Buna Huls 1712) 96.5 96.5cis-1,4-Polybutadiene(Buna CB 10) 30 30Carbon Black ISAF(Corax 6 of DEGUSSA) 75 37.5Finely divided precipitatedsilica (ULTRASIL VN 3 of Degussa) -- 35Mixture of equal parts of precipi-tated silica (ULTRASIL VN 3) andBis-[3-triethoxysilyl-propyl]-tetrasulfide -- 5Zinc oxide 4 4Stearic acid 1.2 1.2Plasticizer (highlyaromatic hydrocarbons 15 15Antiager (N-Iso-propyl-N'-phenyl-p-phenylene-diamine) 1.5 1.5Antioxidant (Phenyl-.beta.-naphthylamine) 1.5 1.5Benzothiazolyl-2-cyclohexylsul-fenamide 1.2 1.2Diphenylguanidine -- 1.5Sulfur 1.6 1.6______________________________________
Mixing Procedure: "Up-side-down"
Premixing in a kneader at 80.degree. C. flow temperature
______________________________________Additive or TreatmentStep 1 Ended-After______________________________________Fillers, chemicals, polymers 0 minutesRam lifted and swept down 3 minutesBatch dumped 3.5 minutesStorage 24 hours______________________________________
Step 2
Final mixing in the kneader at 80.degree. C. flow temperature. Accelerator and sulfur are mixed in in the kneader. Mixing time: 1.5 minutes
______________________________________Properties of the unvulcanized mixtures Mixture 1 Mixture 2t.sub.5 21.7 20.2t.sub.35 27.9 24.2ML 4 65 64sp.gr. 1.16 1.18Properties of the vulcanized mixturesVulcanization temperature: 160.degree. C.Mix-ture VZ ZF M 300 BD E SH EF A T.sup.x)______________________________________1 20 157 65 575 29 57 15 81 1752 20 179 65 600 33 56 19 92 103______________________________________ .sup.x) (stroke 0.250 inches)
Example 12 shows that the organosilanes containing rubber mixtures of the invention may contain advantageously as active filler both silica and carbon black. The properties of both unvulcanized rubber mixtures 1) and 2) are practically the same and show the expert that the silica containing rubber mixture can be used on a large-scale production of tires as well as the carbon black containing rubber mixtures of the piror art.
The properties of the vulcanized mixture containing silica and carbon black show clearly better values in tensile strength, rebound, resistance to tear propagation and heat build-up on dynamic stress than the vulcanized mixture containing only carbon black.

Number	Date	Country
2141159	Aug 1971	DT
2141160	Aug 1971	DT
2212239	Mar 1972	DT

	Number	Date	Country
Parent	529568	Dec 1975
Parent	415176	Nov 1973

Reinforcing additive

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