Abstract:
This invention relates to easily conveyable and easily meterable mixtures having high stability in storage, containing aromatic mineral oils and phenylenediamines, the content of phenylenediamines in the mixture being 1 to 99 wt. %. The mixtures of mineral oils and phenylenediamines according to the invention are used in the production of rubbers and rubber articles.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to easily conveyable and easily meterable mixtures of aromatic oils and phenylenediamines having high stability in storage as well as the use thereof in the production of rubbers and rubber articles. 
     2. Description of the Prior Art 
     The use of phenylenediamines in the production of rubbers and rubber articles is known (see Hofmann, Rubber Technology Handbook, Houser Publishers, 1989, page 268 ff.). The phenylenediamines to be used for the rubber application, which are in the form of solids or viscous melts at room temperature, are generally sold, stored, metered and transported in the form of solids at room temperature or in the form of liquid melts at more elevated temperatures (up to 100° C.). Handling these substances in the form of a liquid melt has the advantage over handling in granular form that melts are dust-free, have a higher density than that of a bed of granules, are capable of being pumped and can therefore be mixed and metered more efficiently. 
     A disadvantage of handling phenylenediamines in the form of low-viscosity melts is the energy consumption and the technical expense which are necessary for the transport and storage of the hot melt. Especially during metering and passage to the mixing apparatus, it is necessary to heat the entire system of ducts because the product instantly crystallises out on being cooled to below the melting temperature and consequently clogs the ducts. 
     The use of aromatic mineral oils in the production of rubbers and rubber articles is also known (see Hofmann, Rubber Technology Handbook, Houser Publishers, 1989, page 296 ff.). 
     The aromatic oils used in the process are generally highly viscous and, in order to lower the viscosity, they are often stored, metered and admixed to the rubber-mixtures at elevated temperatures. 
     It was accordingly the object of the present invention to provide the aromatic oils and the phenylenediamines in an easily transportable and easily meterable form which moreover has a high stability in storage. 
     This object was fulfilled by the provision of the mixtures of aromatic oils and phenylenediamines according to the invention. 
     SUMMARY OF THE INVENTION 
     The present invention accordingly provides easily transportable and easily meterable mixtures having high stability in storage, containing 
     a) aromatic mineral oils and 
     b) phenylenediamines corresponding to the formula ##STR1## 
     wherein 
     R represents an aliphatic C 1  -C 10  hydrocarbon group or a phenyl group optionally substituted with C 1  -C 4  hydrocarbon groups 
     and 
     R&#39; represents hydrogen or an aliphatic C 1  -C 4  hydrocarbon group, 
     the content of phenylenediamines in the mixture amounting to 1 to 99 wt. %. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Aromatic mineral oils which are suitable for the mixtures according to the invention are in particular those having a viscosity-gravity constant of from 0.001 to 1.10, of the type described in Hofmann, Rubber Technology Handbook, Houser Publishers, 1989, pages 296 and 297. Mineral oils having viscosity-gravity constants of from 0.93 to 1.00 are preferably used. 
     Examples of suitable types of mineral oils are listed in Table 1. 
     
                       TABLE 1______________________________________                      Viscosity-gravityName          Supplier     constant______________________________________Sundex 790    Sun Oil      901Ingralen 9290 Fuchs        903Plasticising oil 9215         Fuchs        905Dutrex 726    Shell Chem.  916Dutrex 916    Shell Chem.  921Ingralen 300  Fuchs        922Ingralen 450 (N)         Fuchs        924Renopal 450   FuchsTudalen 370   Dahleke      926Sundex 8180   Sun Oil      928Nuso 250      Esso         928Ingralen 150  Fuchs        929Ingralen 90   Fuchs        930Ingralen 300  Fuchs        933Sundex 890    Sun Oil      936Dutrex 1786   Shell Chem.  937Polymerol 6040         D. Shell     937Dutrex 6 H    Shell Chem.  943Dutrex 1786   Shell Chem.  945Tudalen 85    Dahlke       946Sundex 8125   Sun Oil      949Dutrex R      Shell Int.   949BP Olex RM 35 A         BP           950Ingralen 450  Fuchs        953Plasticiser E 2         Ulitzsch     954Dutrex 757    Shell Chem.  955Naftolen ZD   Metallgesellschaft                      956Plasticiser E 1         Ulitzsch     957Nuso 500      Ess          957Polymerol 6039         D. Shell     963Dealen R 2    DEA          964Naftolen NV   Metallgesellschaft                      964Plasticiser 9230         Fuchs        966Plasticiser oill K         Fuchs        970BP Olex RM 30 BP           971Nuso 40       Esso         975Naftolen H    Metallgesellschaft                      977Exarol 20     Brenntag     980Ingralen 50   Fuchs        983Dutrex 25     Shell Chem.  983Naftolen MV   Metallgesellschaft                      988Ingralen 20   Fuchs        990______________________________________ 
    
     Suitable phenylenediamines corresponding to the above formula are in particular those wherein R represents a methyl, ethyl, isopropyl, 4-methyl-2-pent-2-yl, 5-methylhex-2-yl, propyl, butyl, hexyl group or a phenyl group or tolyl group. Representatives of R&#39; which may be particularly mentioned are hydrogen and the methyl group. 
     The following phenyldiamines are particularly preferred: 
     N-(1,3-dimethylbutyl)-N&#39;-phenyl-p-phenylenediamine (6-PPD), 
     N-(isopropyl)-N&#39;-phenyl-p-phenylenediamine, 
     N,N&#39;-diphenyl-p-phenylenediamine, 
     N,N&#39;-ditolyl-p-phenylenediamine and 
     N&#39;-phenyl-N&#39;-tolyl-p-phenylenediamine, 
     or mixtures of these compounds. 
     The phenylenediamines and the aromatic oils may be used either separately or as mixtures with one another. 
     Depending on the intended use, it may be advantageous to use mixtures according to the invention which contain from 1 to 20 wt. %, from 20 to 70 wt. % or from 70 to 99 wt. % of phenylenediamine in the aromatic oil. 
     Thus a lowering of the viscosity of the aromatic oil is attained by the admixture of about 1 to 20 wt. % phenylenediamine to the aromatic oils. For example, a lowering of the viscosity of the aromatic oil of 50% is attained on admixing 10% of phenylenediamines corresponding to the above formula. A comparable lowering of the viscosity of the aromatic oil without the addition of phenylenediamines is attained only at a temperature of about 15° C. higher. 
     Solutions of phenylenediamine in the aromatic oil which are saturated at room temperature (20 to 80% phenylenediamine solution) can be transferred in liquid form to another vessel, transported, metered and stored and, in contrast to the pure melts, require no heating. The risk of clogging of the ducts in the event of local overcooling of heated melts is also avoided. The solubility in aromatic oils of phenylenediamines corresponding to the general formula (I) is surprising because, for example, 6-PPD does not dissolve appreciably in other plasticising oils conventionally used in the rubber industry; this is illustrated in Example 3. 
     Surprisingly, if about 10% of one of the above-mentioned aromatic oils is admixed to the phenylenediamine melts (99 to 80 wt. % phenylenediamine), the stability of the overcooled melts is increased. Thus, for example, a melt of 6-PPD rapidly cooled to room temperature crystallises out in about 5 to 10 minutes, whereas the addition of 10% of an aromatic oil to the phenylenediamines prolongs their crystallisation times to about 5 to 7 days. 
    
    
     EXAMPLE 1 
     This experiment is intended to show that an admixture of an aromatic oil increases the stability of overcooled melts of PPDs. 
     The mixtures shown in Table 2 were weighed out. Homogeneous solutions were prepared by heating to 80° C. The solutions were then cooled to RT within 3 minutes and the period of time taken for crystals to appear was observed. 
     
                       TABLE 2______________________________________% 6-PPD in    Period of time up toRenopal ® 450         crystallisation______________________________________100%          10 minutes90%           5 to 7 days80%           9 days70%           9 to 14 days60%           9 to 14 days50%           9 to 14 days40%           9 to 14 days______________________________________ 
    
     Comparable effects can be obtained using the mineral oils Naftolen H, Naftolen NV, Naftolen ZD, Exarol oil 20 and Enerflex 656 (Exarol oil) 
     EXAMPLE 2 
     This experiment shows the lowering of the viscosity of the aromatic oil Renopal® 450 by the addition of 10% 6-PPD (Table 3). 
     
                       TABLE 3______________________________________      Renopal ® 450               +10% 6-PDD______________________________________21° C.        18,000     7,100  mPas!40° C.        1,400      75060° C.        320        17080° C.        90         44______________________________________ Renopal ® is a product of the firm Fuchs (Mannheim) having the following physical data: Viscositygravity constant: 0.950 
    
     EXAMPLE 3 
     25% solutions of 6-PPD in Renopal® 450 are prepared at room temperature. Comparison experiment: 6-PPD shows no appreciable solubility in the following plasticising oils used in the rubber industry: 
     Adimoll DO=dioctyl adipate, Bayer AG, Dormagen 
     Mesamoll=alkylsulphonic ester of phenol, Bayer AG, Dormagen 
     Ecubsol oil=alkylate, UK mineral oil plant Wenzel and Weidmann, Eschweiler 
     Exarol oil=from the firm Brenntag