Abstract:
A novel process for making novel naphthalene hydrodimer mixtures which contain PTB in varying amounts and have improved plasticizing properties over PTB alone. The improved plasticizing composition is prepared by contacting a mixture of a hydronaphthalene (e.g., tetralin or an alkyltetralin) and naphthalene or an alkylnaphthalene with a strong acid catalyst. Another embodiment of the invention is the plasticized composition.

Description:
BACKGROUND OF THE INVENTION 
     1-Phenyl-4-(2-tetraly)butane and 1-phenyl-4(1-tetralyl)butane, both known as PTB, are known compounds which are obtained by treating 1,2,3,4-tetrahydronaphthalene (tetralin) with a strong acid catalyst: ##STR1## 
     This reaction is discussed in Ber. 57B, 1990 (1924) and in U.S. Pat. No. 3,336,407 where it is pointed out that not only PTB, but other reaction products as well, such as sym-octahydroanthracene (OHA) and sym-octahydrophenanthrene (OHP) are formed. OHA and OHP are known to be plasticizers for polystyrene (U.S. Pat. No. 2,289,743 and U.S. Pat. No. 2,454,851) but, because of their high volatility they would be of little value for most plasticizer applications in polyvinylchloride (PVC) resins due to unacceptably low levels of permanence resulting from evaporative losses. Also obtained in this reaction is some small amount of 2,6-bitetralyl along with minor amounts of other products. Other related art discussing such reactions is includes L. I. Smith and C. Lo. J. Am. Chem. Soc. 70., 2209 (1948) and U.S. Pat. No. 3,336,407 (1967). 
     PTB has been found to be an effective plasticizer for polyvinylchloride (PVC) resins and such use is the subject matter of U.S. Ser. No. 385,958 filed of even date herewith. 
     BRIEF STATEMENT OF INVENTION 
     This invention relates to a novel process for making naphthalene hydrodimer mixtures which may contain PTB in varying amounts, and, unexpectedly, have improved plasticizing properties. This improved plasticizing composition is an embodiment of the invention and is prepared readily by contacting a mixture of a hydronaphthalene (e.g., tetralin or an alkyltetralin) and naphthalene or an alkylnaphthalene with a strong acid catalyst. Another embodiment of the invention is the plasticized composition. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 lists structures for the major naphthalene hydrodimer types. 
     FIG. 2 lists structures for the secondary naphthalene hydrodimer types. 
     FIG. 3 and FIG. 4 are graphic displays of data obtained. 
     FIG. 5 and FIG. 6 are graphic displays of data similar in nature to FIG. 3 and FIG. 4, but for a different naphthalene hydrodimer within the scope of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred hydronaphthalenes useful in the invention are tetralin and tetrahydroalkylnaphthalenes such as 5,6,7,8-tetrahydro-2-methylnaphthalene and 1,2,3,4-tetrahydro-1-methyl-6-ethylnaphthalene, for example. 
     The other component may, as indicated, be naphthalene or an alkylnaphthalene such as 1-methylnaphthalene, 2,3-diethylnaphthalene and the like. A preferred source of such naphthalenes is the complex mixture of methylnaphthalenes from certain petroleum refinery streams. A still more preferred feedstock can be produced from naphthalene, an alkylnaphthalene or an alkylaromatic petroleum refinery stream high in methyl- and dimethylnaphthalenes by partial hydrogenation so as to produce a mixture of alkyltetralins and alkylnaphthalenes. Alkylbiphenyls and alkylindans, frequently present in mixed methylnaphthalenes petroleum refinery products, may be present and are not necessary undesirable. The feedstock can, of course, be a mixture of two pure hydrocarbons as for example: tetralin plus naphthalene, tetralin plus 1-methylnaphthalene, or 5,6,7,8-tetrahydro-2-methyl-naphthalene and 1-methyl-2-ethylnaphthalene. As is evident from the above, the alkyl substituent on the tetralin or naphthalene rings will be a lower alkyl group. 
     Catalysts which may be used for this reaction include Bronsted acids such as HF and especially HF/BF 3  mixtures; Lewis acids such as AlCl 3  and AlCl 3  /HCl mixtures and solid catalysts such as acidic &#34;Y&#34; type or any of the more acidic types of the Mobil ZSM series of synthetic shape-selective zeolites. Other strong acid catalysts may be used such as those which are effective for transalkylation reactions such as the commercially significant transalkylation of diethylbenzene with benzene to yield ethylbenzene. An alumina-BF 3  catalyst is useful for such transalkylation. Because hydrogen transfer processes play a significant role in the process of this invention, dual-function catalysts may be preferred. By dual-function catalysts is meant catalysts which combine high acidity with hydrogenation capability; for example: platinum on alumina, palladium on acidic &#34;Y&#34; type synthetic zeolite, nickel on silica-alumina and the like. Zeolite type catalysts are preferred for the reaction. 
     The products obtained by the above described reaction are always naphthalene hydrodimer mixtures even when pure feedstocks are used, as can be seen in Table I. By the term naphthalene hydrodimer we mean any C 20  hydrocarbon which can formally be considered a dimer of naphthalene but which contains a higher hydrogen to carbon ratio than naphthalene (C 10  H 8 ). Because of the extensive hydrogen transfer activity which is characteristic of the process of this invention, the actual naphthalene hydrodimer mixtures produced may also contain minor amounts of naphthalene dimers (C 20  H 16 ), such as phenyltetrahydrophenanthrene, and naphthalene dehydrodimers, such as binaphthyl (C 20  H 14 ) and perylene (C 20  H 14 ) The primary naphthalene hydrodimers are also subject to a variety of secondary reactions such as isomerization, transalkylation, hydrogen transfer, cyclization, disproportionation, and the like, which can lead to the formation of C 18 , C 24 , C 28 , and C 30  hydrocarbons (also with varying hydrogen to carbon ratios). FIGS. I and II provide a partial list of the types of naphthalene hydrodimers and associated secondary products which characterize the &#34;naphthalene hydrodimer mixtures&#34; produced by the process of this invention. 
     
                                           TABLE I__________________________________________________________________________COMPOSITION OF HYDRODIMER FRACTION OF PRODUCT OF REACTION OF TETRALINWITHVARIOUS AROMATIC SUBSTRATES AT 125° C. WITH 2 WT. PERCENTAlCl.sub.3 (IN WEIGHT PERCENT OFINDIVIDUAL COMPONENT TYPE BY MASS SPECTROSCOPY).      Aromatic Substrate                                           Refinery                                                  Refinery      Emperical Formula of                 Stream &#34;A&#34;                                                  Stream &#34;B&#34;      Unmethylated Parent                 Tetralin    1-Methyl-                                    2-Methyl-                                           (80% Methyl-                                                  (50) Methyl-Hydrodimer Type      Hydrocarbon                 Alone                      Naphthalene                             naphthalene                                    naphthalene                                           naphthalenes)                                                  naphthalenes)__________________________________________________________________________Phenyltetralylbutane      C.sub.20 H.sub.24                 66.0 4.5    4.3    4.5    3.2    4.8Bitetralyl C.sub.20 H.sub.22                 23.2 6.6    7.0    8.2    4.1    5.8Phenylnaphthylbutane      C.sub.20 H.sub.20                 2.4  30.6   24.0   27.0   20.1   24.3Tetrahydrobinaphthyl      C.sub.20 H.sub.18                 2.4  50.7   51.9   53.0   49.3   49.0Tetrahydroperylene      C.sub.20 H.sub.16                 3.6  2.1    3.2    2.5    8.5    7.8Binaphthyl C.sub.20 H.sub.14                 --   2.4    5.1    2.3    8.0    6.2Perylene   C.sub.20 H.sub.12                 2.4  3.1    4.5    2.5    6.8    2.1__________________________________________________________________________ 
    
     In accord with the present invention, when a mixture of naphthalene and tetralin are contacted with a sufficiently strong acid catalyst a decidedly different reaction sequence predominates that when tetralin alone is so treated resulting in the formation of a very different product having different physical properties including improved ability to plasticize polyvinyl chloride. While tetralin alone initially yields phenyltetralylbutane which is subsequently converted into octahydroanthracene, octahydrophenanthrene, diphenylbutane and benzene, an equimolar mixture of tetralin and naphthalene gives hydrogenated binaphthyls as the predominate hydrodimer type along with lesser amounts of phenylnaphthylbutane and only minor amounts of phenyltetralylbutane. Table I provides a detailed description of how the nature of the components of the hydrodimer fraction depends on the type of aromatic substrate with which the tetralin is reacted. Furthermore, the tendency of the intially formed hydrodimers to react further and yield low molecular weight disproportionation products is significantly diminished when a mixture of naphthalene and tetralin is the reactant. This latter effect is still more pronounced when 1- or 2-methylnaphthalene or the mixture of mono- di- and trimethylnaphthalenes in certain selected aromatic-rich petroleum refinery streams are used instead of naphthalene, as shown by the data in Table II. 
     
                       TABLE II______________________________________OVERALL CONVERSION AND SELECTIVITIES TOMAJOR PRODUCT FRACTIONS IN THE REACTION OFTETRALIN WITH VARIOUS AROMATIC SUBSTRATESAT 125° C. WITH 2 WT. PERCENT AlCl.sub.3 (IN MOLEPERCENT BY GAS CHROMATOGRAPHY)           Selectivity To:                         Dispro-                         portion-                                High Mol.        Conver-  Hydro-  ation  Wt.Substrate    sion     dimers  Products                                Products______________________________________Tetralin Alone        27.7     37.2    59.5   3.3Tetralin With:Naphthalene  26.6     70.5    13.5   16.01-Methylnaphthalene        21.8     78.2    11.0   10.82-Methylnaphthalene        17.7     86.0    6.7    7.3Refinery Stream &#34;A&#34;        14.9     94.0    4.0    2.0Refinery Stream &#34;B&#34;        9.4      100.0   nil    nil______________________________________ 
    
     When methylnaphthalenes and/or methyltetralins are used as feedstocks the methyl groups become distributed over all the rings of the products as a result of transalkylation and hydrogen transfer processes. Because of these concurrent reactions, alkylnaphthalenes and/or alkyltetralins yield quite complex product mixtures. 
     The process of the invention is readily carried out under relatively mild temperature conditions, preferably at the reflux temperature of the hydrocarbon mixture being used. Such temperature will range from about 200° to about 350° C. Most preferably, the reaction is carried out simply by refluxing the vapors of the hydrocarbon mixture over a bed of the acid catalyst. In this way the reactants and products have minimal contact with the acid and the product becomes concentrated in the container in which the reaction mixture is heated. The product in the container may be distilled to remove any lower boiling unreacted starting materials and the higher boiling product mixture of hydrodimers thereby obtained. Another alternative procedure of operation is to carry out the reaction in the vapor phase by simply passing vapors of the reactants over the catalyst. 
     The naphthalene hydrodimer mixtures which are produced by the process of this invention exhibit a surprisingly good compatibility with polyvinyl chloride resins and also have reasonable plasticization efficiency. This combination permits these products not only to be used at high replacement levels (i.e., from about 50% to about 90%) as secondary plasticizers, but even to be used as primary plasticizers. Because these products are made from low-value refinery streams by simple processing operations, they are less expensive to produce than conventional ester plasticizers such as di(2-ethylhexyl) phthalate, for example and, while they are less efficient than ester plasticizers, they are sufficiently less expensive to render them cost-effective as partial replacements or substitutes for ester plasticizers. 
     EXAMPLE 1 
     Preparation of HCP-300 (tetralin and naphthalene) 
     A mixture of 2563 g. (20.0 moles) of naphthalene and 2644 g. (20.0 moles) of tetralin was charged to the pot of a straight-through (non-siphoning) extraction apparatus. In the thimble of the extractor was placed 165 g. of Linde LZ-Y82 &#34;Y&#34; type zeolite catalyst in 1/16&#34;×1/8&#34; extrudate form. The hydrocarbon mixture was refluxed so that the refluxing naphthalene and tetralin trickled through the catalyst bed heated by the rising vapors. The mixture was refluxed until a conversion of approximately 85 percent was achieved. This was indicated by an increase in the pot temperature from the original 210° to about 300° C. Periodic gas chromatographic analysis of the pot contents was also used to monitor the conversion level. 
     Distillation of the product in a 20-plate Oldershaw column at atmospheric pressure removed the unreacted naphthalene and tetralin and a small amount of low molecular weight by-products. The main product, amounting to 3082 g., was distilled at 1 mm of Hg over the range of 180° to 200° C. The molecular weights of the components of this naphthalene hydrodimer product fall in the range of 252 to 272 according to a low ionizing voltage mass spectrogram. 
     EXAMPLE 2 
     Preparation of HCP-400 (tetralin and Sure Sol®-180; a mixture of at least 80% by weight of methylnaphthalenes and the remainder comprising alkylbenzenes, indanes and biphenyls) 
     A mixture of 2842 g. of a refinery stream concentrate comprising about 80 percent mono-, di- and trimethylnaphthalene isomers and about 20 percent of other alkylaromatic hydrocarbons with 2644 g. of tetralin was reacted over Linde LZ-Y82 catalyst in the same manner as the above example. The 85-90 percent converted mixture was distilled to yield 2750 g. of a methylated naphthalene hydrodimer product boiling in the range of 190° to 250° C. @1 mm of Hg. The molecular weights of the components of this product fall in the range of 252 to 314. 
     The hydrodimer products of the process of the invention are viscous, water white, light yellow or amber colored liquids which boil over a range of from about 170° to about 220° C. at 1 mm Hg. These products are readily incorporated into PVC by milling it into sheets of the resin in accord with conventional procedures. 
     The attached tables provide data on the properties of poly(vinyl chloride) sheets compounded with varying levels of di(2-ethylhexyl) phthalate and two different hydrocarbon mixtures of the invention. 
     
         ______________________________________Summary of Tensile Datafor HCP-300 Replacement of DOP______________________________________Total %       Ten-                   Mod-  @Plasti- DOP     sile          % Elongation                                ulus  100%cizer Re-     Ini-   Strength                       Ini-       Ini-  Elong.(PHR) placed  tial   Aged   tial Aged  tial  Aged______________________________________30     0      2825   3025   250  200   2525  2800         2825   2975   275  200   2450  2750         2925   2950   275  200   2550  2675         2900   3025   300  200   2425  282538    21      2875   2775   300  250   2200  2350         3000   2825   300  275   2250  2350         3075   2975   300  275   2250  2550         2950   2775   250  275   2250  230050     0      2500   2525   300  300   1400  1650         2575   2375   300  300   1450  1500         2575   2400   350  300   1350  1500         2575   2425   325  325   1400  142550    40      2775   2600   375  250   1600  1875         2850   2625   375  250   1600  2000         2725   2775   375  300   1575  1950         2800   2725   350  275   1575  200060    50      2400   2500   300  300   1175  1550         2425   2500   325  300   1300  1575         2450   2525   350  300   1200  1650         2575   2475   375  275   1200  160070     0      2125   1975   475  475    750   800         2125   1850   450  475    825   750         2125   1975   475  450    775   800         2075   1950   450  450    750   80070    20      1950   2250   350  400    875  1150         2200   2175   450  400    800   950         2225   2150   450  400    825  1000         2300   2200   450  450    825   87570    40      2350   2300   400  350    975  1175         2300   2225   400  350    850  1100         2300   2275   400  375    975  1100         2200   2175   400  350    900  102570    57.1    2350   2325   400  300   1050  1325         2500   2250   400  300   1175  1200         2475   2250   400  300   1075  1250         2475   2350   400  325   1050  115070    70      2400   --     425  --    1000  --         2525   2275   400  325   1150  1225         2525   2150   425  300   1175  1100         2450   2250   375  300   1100  130070    80      2525   2400   400  200   1325  1800         2525   2400   400  275   1300  1550         2575   2350   400  250   1325  1550         2525   2475   375  300   1300  155070    90      2425   2200   350  200   1300  1850         2450   2325   375  300   1275  1500         2400   2275   375  250   1350  1550         2400   2325   350  250   1350  160070    100     2400   2000   375  100   1300  2000         2425   2200   375  150   1450  1900         2450   2275   350  175   1550  1950         2450   2350   350  150   1550  207580    62.5    2225   2025   400  225    875  1150         2325   2125   425  325    925  1075         2200   2100   375  350    925  1000         2300   2075   400  325    925  1100______________________________________TotalPlasticizer   % DOP      Initial Initial    Initial(PHR)   Replaced   Tensile % Elongation                                 Modulus______________________________________50       0         2200    375        1175              2100    350        1175              2150    375        1150              2175    400        105050      20         2350    350        1400              2250    350        1300              2925    350        1625              2700    325        155050      40         3125    350        1775              2950    375        1750              3000    375        180050      60         3175    325        2275              3100    300        2250              3100    275        222550      80         3175    300        2550              3175    300        2525              3150    275        2570              3075    2 5        255050      100        3225    250        2975              3225    225        3050              3000    300        2875              3000    300        290040       0         3125    325        1950              3050    300        2050              2900    300        205040      100        3650    200        3650              3850    225        2850              3600    250        360030       0         3700    275        3100              3625    300        2950              3675    275        3000______________________________________Plasticizer     % DOP    Hardness      Volatility(PHR)     Replaced Initial   Aged  (%)______________________________________30        0        91.6      75.3  0.2830        100      --        85    2.6238        21       92.3      88.0  1.0940        0        81.0      78.0  0.2340        100      94.7      86.7  3.4050        0        76.5      74.7  1.4950        20       76.3      75.7  1.9850        40       77.2      72.5  3.5450        60       82.6      69.7  2.2750        80       85.3      83.0  2.1650        100      92.0      93.0  3.0460        50       73.0      70.3  5.0370        0        66.3      65.0  1.7570        20       65.3      66.7  3.2570        40       65.3      69.3  4.5870        57.1     68.7      70.3  5.5070        70       69.8      73.2  6.9370        80       71.0      76.3  6.2970        90       71.0      74.5  6.1470        100      76.5      79.0  6.7580        62.5     65.0      66.3  4.92______________________________________Total %       Ten-                   Mod-  @Plasti- DOP     sile          % Elongation                                ulus  100%cizer Re-     Ini-   Strength                       Ini-       Ini-  Elong.(PHR) placed  tial   Aged   tial Aged  tial  Aged______________________________________30    0       3325          250        2825         3350          300        2750         3150          275        252538    21      3150          300        2175         3275          350        2175         3175          350        215050    0       2375          275        1375         2375          300        1325         2425          300        137550    40      2925          350        1700         2750          300        1650         2850          300        165060    50      2800          400        1275         2650          350        1350         2750          375        130070    0       1700          375         675         2000          400         775         2025          400         80070    20      2275          400         900         2350          400         950         2275          350         95070    40      2375          350         875         2350          350        1025         2350          325        100070    57.1    2525          375        1100         2575          400        1100         2450          350        110070    70      2575          425        1125         2400          350        1175         2550          400        117570    80      2550          400        1275         2700          375        1400         2600          400        127570    90      2550          375        1425         2500          350        1350         2550          400        127570    100     2600          375        1725         2575          350        1650         2550          300        1650______________________________________ 
    
     The above data is best evaluated by reference to the graphic displays of FIG. 1, FIG. 2, FIG. 3 and FIG. 4. 
     These figures provide a graphic display of the way the key tensile properties (ultimate tensile strength, elongation at break and tensile modulus at 100 percent elongation) are distributed over a broad range of PVC formulations incorporating the naphthalene hydrodimer mixture as hydrocarbon plasticizers. Data is given for PVC plasticized with DOP in which amounts of the DOP varying from 0 to 100 percent have been replaced by the compositions of this invention and for amounts of total plasticizer (combined DOP and compositions of the invention) varying from 30 to 80 parts per hundred parts by weight of PVC resin. Thus, the data at 70 PHR and 60 percent replacement are for a formulation containing 100 parts PVC resin, 28 parts DOP and 42 parts of the compositions of the invention. As long as the plasticizer remains fully compatible with the resin at the level used, the tensile modulus at 100 percent elongation (FIGS. 1 and 3) provides a good indication of the plasticization efficiency of the plasticizer; the lower the value at a given loading, the softer and more flexible is the formulation. By comparing the values for formulations plasticized by DOP alone (0 percent replacement) with those of formulations containing the compositions of the invention, it is seen that the values increase steadily as the amount of DOP replaced by the compositions of the invention increases. This shows that DOP is the more efficient plasticizer. However, the rather small increases in tensile modulus as shown by the numbers in the boxes (especially at replacements below 50 percent) indicates that the plasticization efficiency of the compositions of the invention are not notably inferior to that of DOP. 
     FIGS. 2 and 4 display the tensile strength and elongation at break of the same PVC formulations represented in FIGS. 1 and 3. The constancy of these values over the total range of replacement of DOP by the products of this invention is good indication of the compatibility of the products of the invention, and their mixture, with DOP with PVC resin in these formulations and other more qualitative tests corroborate the good efficiency of the products of the invention as a PVC plasticizer. Thus, the appearance, feel, lack of color, and other general qualitative properties all establish the good compatibility and plastization efficiency of the products of the invention for PVC.