DE2133150A1 - Vulcanised rubber goods - contg finely dispersed crosslinked elastome - Google Patents

Abstract

Vulcanised rubber goods, esp. suitable for pneumatic and solid tyre side walls and treads, conveyor belts, elastic couplings, cushioning elements, and high resistant to cut growth under dynamic stresses are prepd. from compsns. contg. 10-40 (20-30) wt. % finely dispersed particles of crosslinked or partly crosslinked elastomers, (I), in addn. to basic mixt. of natural and/or synthetic elastomers and usual light-, ageing- and fatigue-stabilisers, fillers and vulcanising agents (where wt. % (I) is calculated w.r.t. rubber components in initial mixt.). Pref. (I) are highly satd. polymers, esp. vulcanised rubber mixtures (e.g. wastes or regenerates) contg. fillers and mixing components, and partic. powdered resin crosslinked butyl rubber vulcanisates.

Description

Rubber vulcanizates with high resistance to crack growth dynamic stress The invention relates to rubber vulcanizates of high resistance against crack growth under dynamic loading.

The fatigue cracking and the growth of cracks formed any Origin occur in particular with prolonged dynamic loads on, with the cracks perpendicular to the direction of stress due to elongation, compression or shear and increase as the load continues and also become more numerous.

Depending on the dimensions of the item used and the rest Conditions lead the fatigue cracks to total failure. So far it is of the opinion that the fatigue cracking depends on a number of different factors, such as B. the ambient temperature, the oxygen concentration, the amplitude of the mechanical stress and its frequency, the geometric shape of the stressed Object and the like.

It appeared desirable the resistance to cracking and especially against the crack growth of rubber vulcanizates, especially dynamic claimed rubber vulcanizates, such as. B. vehicle tire sidewalls, continue to improve.

It has been found that rubber vulcanizates have high resistance to the growth of the ria can be obtained under dynamic loading when the production of the vulcanizates cross-linked rubber compounds used in their manufacture or partially crosslinked elastomers are added after the end of the mixing process as a particle. are contained in finely dispersed distribution in the mixture.

Such a finely dispersed distribution is obtained when the addition takes place in the form of powdery vulcanizates - this is particularly the case with the Use of butyl rubber and / or EPDM vulcanizates is the case - or if the Vulcanizates to be added previously replasticated on a folding unit in a manner known per se have been.

Those accruing from rubber processing are preferably used Vulcanized waste and / or regenerated highly saturated polymers such as Butyl rubber, ethylene-propylene terpolymers, polyurethane rubber and the like.

The cross-linking system that is used in the manufacture of the vulcanizate powder or -replastikate was used, has no significant influence on the Crack growth-inhibiting effect of the powders or plastics added according to the invention; The grain size of the vulcanizate powder used can also vary within wide limits. Powders of high fineness are preferred, especially those that have a sieve with a Mesh size of 0.2 mm pass.

It can be assumed that under dynamic stress Cracks from rubber vulcanizates when they hit dispersed particles of the type described are at least greatly hindered in their further crack growth, by the peak stresses concentrated in the crack, which are responsible for the further tearing in preferred directions are responsible for being distributed or degraded on the particles will.

Finely ground ones are particularly suitable for the crack protection effect described Vulcanized, but also plastic and regenerated from cross-linked mixtures on the Based on highly saturated polymers such as butyl rubber, chlorobutyl rubber, Ethylene-propylene terpolymers; but also with crosslinked polyurethane elastomers, Recycled polychloroprene, chlorosulfonated polyethylene vulcanizates and - in to a lesser extent - even with non-chemically cross-linked, but via highly active fillers stabilized elastomer batches an improvement in durability against crack growth under dynamic loading, provided these substances are no longer completely homogeneous when incorporated into the basic mixture, but dispersed.

The base mix, i.e. H. So the conventional way against aging and light cracks stabilized rubber compound can be based on natural rubber and / or synthetic rubber.

The test for crack growth under mechanical stress is generally carried out in accordance with DIN 53522. Here, the crack growth is one through The crack produced by the puncture was determined from 2 to 4, from 2 to 8 and from 2 to 12 mm.

While mixtures based on natural rubber-polybutadiene blends for example, for a crack growth of 2 to 4 mm 7 x 103, a crack growth of 2 to 8 mm 20 x 103 and for one from 2 to 12 mm hardly more than 40 x 103 bends claim, need appropriately constructed mixtures, the additional 20 to 30 percent by weight - based on the polymer content of the base mixture - of grinding dust or plasticate contain considerably higher buckling numbers to achieve the same Crack lengths.

The mixtures constructed according to the invention have particular advantages zù use for the production of pneumatic vehicle tires, especially their side walls and treads, from solid tires, conveyor belts, elastic couplings, damping elements and the same.

The invention is explained in more detail in the following exemplary embodiments A basic mixture consisting of natural rubber-polybutadiene blend 100 parts by weight Protective agent mixture of N-phenyl-N'-isopropylp-phenylenediamine and N-phenyl-N '- (1,3 Dimethylbutyl) -p-phenylenediamine 3 I1 HAF carbon black LFo 11 other components of the mixture (Processing aids, etc.) 13.1 sulfur 2.5 combined mercapto / surerami - -Accelerator 0.5 became the vulcanizates listed below the specified amount and the specified condition mixed up.

Type of vulcanizate Type of cross-linking Condition form Additional quantity (K%) A) Butyl, soot-filled, resin-crosslinked grinding powder 20 B) Butyl, soot-filled, resin-crosslinked Grinding powder 30 C) butyl, filled with resin, resin-crosslinked plastic 20 D) butyl, filled with soot sulfur-crosslinked regenerate 20 E) EPTR, * soot-filled peroxide-crosslinked plasticate 20 * F) EPTR, carbon black-filled, sulfur-crosslinked, plastic 20 G) polychloroprene through metal oxides Regenerate 20 containing filler H) Polyurethane rubber peroxide cross-linked Regenerate 20 * Ethylene-propylene terpolymer The following vulcanizate characteristics for vulcanization of 50 minutes at 1340 C were determined for the individual blends: Basic mixture with the addition of: Basic A B C D E F G H mixture Festigy.

(kp / cm) DIN 53504 240 215 188 185 190 1) 0 210 215 200 elongation (%) DIN 53504 600 580 590 560 600 670 620 660 570 Clamp.

b. 3002% (kp / cm) 85 75 65 70 65 5 ° 67 59 Shore hardness A 59 58 60 59 56 54 57 55 58 Elast. (%) DIN 53512 54 43 39 46 48 53 58 51 48 Very dispersion very very very of the accessories - fine fine coarse fine fine fine fine fine Crack growth according to DIN 53 522 (with a given groove) the number of kinks is given (x 103) with crack expansion of: Basic mixture A B 0 D E F G H 2 - 4 mm: 7 10 35 10 20 22 8 25 11 2 - 8 mm: 20 120 200 105 165 155 75 160 95 2 - 12 mm: <40> 300 »300 270» 300> 300 250 -280 180 The opposite of the pure one is clearly recognizable Base mixture significantly reduced the rate of growth of the cracks that develop is inversely proportional to the number of buckling up to a certain crack length.

Claims (5)

Patent claims: Ü Rubber vulcanizates of high resistance to crack growth under dynamic stress from rubber compounds based on natural and / or synthetic elastomers with the addition of customary light, aging and anti-fatigue agents, fillers, vulcanizing agents, and the like, thereby characterized in that the rubber mixtures are finely dispersed in particles contain crosslinked or partially crosslinked elastomers. 2. vulcanized rubber according to claim 1, characterized in that the rubber mixtures in finely dispersed distribution of crosslinked or partially crosslinked particles contain highly saturated polymer. 3 .. rubber vulcanizates according to claims 1 and 2, characterized in that that the rubber mixtures in a finely dispersed distribution of particles von.vulkanisiert Contain rubber mixtures, which in turn contain fillers and conventional mixture components contain. 4. Rubber vulcanizates according to Claims 1 to 3, characterized in that that the rubber mixtures are pulverized, resin-crosslinked butyl rubber vulcanizates contain. 5. rubber vulcanizates according to claims 1 to 4, characterized in that that they have a proportion of 10 to 40, preferably 20 to 30 percent by weight - based on the rubber component of the starting mixture - on crosslinked or partially crosslinked Contains elastomers.