812
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 18. No. 8
Furfural Derivatives as Rubber Accelerators' By J. P. Trickey and G. J. Leuck THE MINERLABORATORIES, CHICAGO, ILL.
HE steadily decreasing cure effect, however, is much A review is given of the results reported in the literaprice of f u r f u r a l i s less with hydrofuramide than ture on the use of furfural derivatives as rubber acrapidly increasing its w i t h e i t h e r of t h e others. celerators. The accelerating action of hydrofuramide, The effect on the color of the use and that of its derivadithiofuroic acid, and its lead and zinc salts has been tives in industrial processes. cured rubber is practically the studied in some detail. The results show that hydrosame when the pieces are first Among the derivatives are a furamide is less active than hexa or diphenylguanidine, cured, but on aging a brownnumber that have marked while the thio acid and its salts are of the ultra-acaccelerating action on the ish color is developed when celerator type. Mention is made of other types of vu1 c a n i z a t i o n of rubber. hydrofuramide is used which compounds and possibility of preparing many accelerThe range of activity is wide, would limit its use to dark ators of a wide accelerating range is pointed out. stocks. The results obtained v a r y i n g f r o m t h e ultraaccelerator type to the type in cures at 60 pounds steam for which relatively high temperatures are necessary for the pressure (307" F.) are given in Table I and the results a t 50 pounds steam pressure (298' F.) in Table 11. accelerating action to be manifested. Hydrofuramide, which has been sold in France under the Table I-Cure a t 60 Pounds Steam Pressure (307O F.) trade name of Vulcazol, is perhaps the best known of the ~ - 4 . 5 % - -1.0%--1.5%---. ~ 2 . 0 % - Time TenTenTenTenaccelerators derived from furfural. DuboscZ and Ricard3 Min. sile Elong. sile Elong. sile Elong. sile Elong. report a good cure in 10 to 20 minutes a t 136' C. using 0.5 Hydrofuramide to 1.0 per cent of hydrofuramide in a high zinc batch with 4 15 1563 950 900 1981 900 2195 850 1552 30 1689 850 2201 900 2336 850 2558 850 to 5 per cent sulfur, obtaining under these conditions a ten45 1826 850 850 2301 800 2581 800 2222 60 2192 900 sile of 3000 to 3600 pounds per square inch. Twiss4 obtained 2124 850 2244 800 2261 750 75 2315 900 2033 800 maximum tensile of 2000 to 2200 pounds per square inch 90 2174 900 1939' 800 105 2177 850 1801 750 using a low zinc (1 to 5 per cent), 10 per cent sulfur, and 1 120 1960 850 1560 750 per cent hydrofuramide in 45 minutes a t 138" C. Hexamethylenetetramine Furfurin has accelerating action very similar to that of 4.25y0- ,0.57,-4.757,- -i.07~-15 850 2332 850 1517 900 850 2209 1829 hydr~furamide.~ 30 2044 850 2495 800 2609 800 3148 800 A number of accelerators occur among the sulfur deriva45 2539 700 2359 850 750 800 2646 2782 60 482 400 1564 700 599 400 663 500 tives. A patent has recently been issued to Cadwells on Difihenylguanidine the use of thiofurfural as an accelerator. Bruni6and Romani' 4.5704.75707 1 .O%4.2570report the ultra-accelerating action of dithiofuroic acid, but 15 1929 850 2429 800 3087 750 2959 700 2799 650 30 2415 800 2746 750 2916 700 give no numerical data. 1846 600 45 2558 750 2391 750 2304 650 60 2235 750 1979 700 1756 650 1647 600 I n addition to these covering the accelerating action of furfural derivatives, patents have been granted to Trumbull Table 11-Cure a t 50 Pounds S t e a m Pressure (298O F.) and Winkelmanns on the use of resinous reaction products of -2.0%A. 5%-1 .O%--, -1.5%the guanidines with furfural as age resistors, and to WinkelTime TenTenTenTenMin. sile Elong. sile Elong. sile Elong. sile Elong. mann and Gray9 on the use of condensation products of furHydrofuramide fural with a-naphthylamine and o-toluidine for the same 850 2219 1861 850 1133 850 305 800 15 purpose. Winkelmannlo has also been granted a patent on 2407 850 2282 850 900 850 1653 30 1014 850 2546 800 2286 850 45 1372 950 1854 the use of furfural-0-toluidine in the production of renewed 750 800 2340 850 2286 2225 60 1518 900 800 800 2457 850 2398 850 2300 75 1559 rubber. 800 800 2240 2187 850 1950 850 90 1719
T
Experimental
An investigation of the possibilities of furfural derivatives as accelerators has been begun in this laboratory. Early in the experimental work the accelerating action of hydrofuramide, hexa, and diphenylguanidine was compared. The formula used in these experiments, as well as in all the others reported in this paper, was 100 parts rubber (smoked sheets), 10 parts zinc oxide, and 5 parts sulfur. Hydrofuramide was found to be roughly one-third to onehalf as effective as hexa and diphenylguanidine. The over1 Presented before the joint meeting of the Division of Rubber Chemistry and the Akron Section of the American Chemical Soriety, Akron, Ohio, February 22 and 23,1926. 1 Caoutchouc & gutta-percha, 17, 10495 (1920). U. S. Patent 1,440,176 (1922). 4 J . Soc. Chem. I n d . , 40, 2421' (1921). 6 U. S. Patents 1,564,824 and 1,564,825 (1925). 8 I n d i a Rubber J . , 64, 937 (1922). 7 Caoutchouc & gutta-percha, 19, 11626 (1922). a U.S. Patent 1,496,792 (1924). * U. S. Patent 1,515,642 (1924). 10 U. S. Patent 1,532,218 (1925).
105 120
15 30 45 60 75 90 105 120
15 30 45 60 75 90 105 120
1794 1846
850
850
4.25%$07 800 la62 950 1935 850 2210 850 2468 800 2397 800 7 50 2333 1901 750 4.25% ,"1418 950 850 2062 2311 850 2455 800 800 2368 2438 800 2188 800
2167
800
800 2128 2249 1930 800 2324 Hexamethylenetetramine
4.5%1197 950
800
800
4.75%-
1450 950 900 1959 900 2354 850 850 2728 2412 2930 800 2975 850 2676 700 2953 800 2676 750 2419 750 500 734 2131 650 608 500 1651 6 50 Diphenylguanidine 4.5%4.7570800 850 2322 2024 2875 750 2264 750 700 2963 2793 750 700 2705 2628 750 2664 700 2943 7 50 2425 700 700 2692 1844 700 700 2055 1655 650 700 1900
2140 2165
SO0
800
-1.0%1446 2543 2862 2853 2450 1225
535 435
900 850 800 750 650 600 400 400
- 1 . 0 % ~ 2723 2779 2949 2542 2115 2064 2104 1580
800 700 700 650 600 600 650
600
The effect of furfurin was also studied and found to be practically the same as that of hydrofuramide. A number of other furfural derivatives have been tested for accelerating action. Because of the ease with which furfural condenses with other compounds to form resinous
I
INDUSTRISL A-VD ESGINEERING CHEMISTRY
August, 1926
bodies, a substantial number of the compounds studied were of this type. Among these may be mentioned the condensation products with aniline, diphenylaniline, and dimethylaniline. I n general, in this limited experimentation, the products formed with aromatic compounds have a relatively small accelerating action while those with aliphatic compounds have considerably more. A number of the thio aldehydes having the empirical formula (C4H30.CHS)=have been reported in the literature. Only two have been prepared in the pure state, both of which had the formula (CdH30.CHS)3, but differed markedly in their properties. Others of resinous nature have been made with formulas of (CaH30.CHS)18 - M. Two thio aldehydes, one liquid and the other solid, were prepared and tested by the writers. The results obtained using the two thio aldehydes as well as ethyl furylamine and furylidine ethylamine, when cured at 50 pounds steam pressure, are given in Table 111. These compounds were picked from a number of the furfural derivatives tested as they were of nonresinous type with definite physical characteristics.
Time Min. 15 30 45 60
Table 111-Cure a t 50 Pounds Steam Pressure (298O F.) 1% ETHYL 1% FURYLIDINE 1% THIOFUR- 1%THIOFURFURYLAMINE ETHYLAMINE FURAL 1 (SOLID) FURAL 11 (LIQUID) TenTenTenTensile Elong. sile Elong. sile Elong. sile Elong. 1148 1000 1402 900 122 500 198 700 1864 950 2231 900 542 800 883 850 2218 850 2579 850 1149 900 1644 900 2247 800 2670 800 1190 800 1019 750
Work in this laboratory has been directed primarily to the study of sulfur derivatives, and dithiofuroic acid and its salts have been studied in some detail. These compounds are of the ultra-accelerator type, giving cures comparable with those obtained by the use of tuads. A comparison of the results obtained using dithiofuroic acid, zinc dithiofuroate, lead dithiofuroate, and tuads when cured a t 5 pounds steam pressure, is shown in Table 11'. The proportions of 0.8 per cent zinc and 1.0 per cent lead dithiofuroate are roughly equivalent to 0.6 per cent of the free dithiofuroic acid. Table IV-Cure a t 5 Pounds Steam Pressure 6%-0.8 %--0.4%Time TenTenTenMin. sile Elong. sile Elong. sile Elong. Dithiofuroic Acid 10 1489 900 2916 900 20 4198 850 4313 2680 900 850 3362 30 4329 850 4332 850 850 40 4341 4454 3592 850 850 850 50 4012 3562 850 800 850 4190 60 4185 3679 850 800 800 4217 90 4062 3669 850 800 800 4203 3557 120 4020 800 850 4081 800 Z i n c Dilhiofuroate 70.4%4 . 6 % ~-0.8%7 1907 950 2574 830 2722 850 3266 15 860 4114 860 4076 800 22 3932 860 4317 4219 820 783 30 3900 850 3985 800 4138 750 3900 810 45 3795 810 4084 753 60 3420 3695 765 2847 715 830 3406 90 3537 760 2812 820 680 3170 2488 120 730 2166 830 650 Lead Dilhiofuroate 15 30 45 ~. 60 ~-0.4%10 15 22 30 45 60
2825 3511 4373 4275 3868
847 840 790 765 695
Tuads 4.6%3034 830 4481 812 4673 745 4274 695 3750 645 2929 573
4.8% 3217 4792 4562 4187 3386 3454
810 797 760 720 643 615
(227O F.)
c-l.O%-Tensile Elong. 3817 4374 4510 4411 4466 4435 4345 4248
850 850 850 800 800 800 800 800
--1.0%3170 825 4180 813 3334 700 3566 700 3297 683 650 2766 3070 693 -814 500 -1.0%4185 4289 4248 4037
815 789 745 735
-1.0%3073 4740 4639 4551 3980 3323
840 780 783 725 670 623
The effect of temperature on the accelerating action of dithiofuroic acid is shown in Table V
813
of Temperature on Cure-Dithiofuroic Arid (Averages of several runs) 5 L s s STEAM 1OLss STEAM 2OCss STEAM (227' F ) (239O F ) (258' F ) Tensile Elong. Elong. 0 4 Per cent
Table V-Effect Time 5 7 10 20 30 40 45 50 60 120 5 7 10 20 30 40 45 50 60 90 120
5 7 10 20 30 40 45 50 60 90 120
2680 3362 3592
900 850 850
3562 3679 3669
850 850
3557
850
1489 4198 4329 4341
900 850 860 850
4012 4185 4062 4020
800 800 800 800
2916 4313 4332 4454
900 850 850 850
4190 4217 4203 4081
850 800 800 800
3817 4374 4510 4411
850 850 850 800
4466 4435
800 800
4248 4345
8oo 800
5
7 10 20 30 40 45 50 60 120 90
900 875 875 850
1885
950
2593 2534 2351
925 925 925
3332
850
2370
3267 3191
850 850 850
2241 2071 1936
850 850 850 850 825
2956
875
3607 3389 3168
875 875 875
1311 2358 3500 3333
2890 0 . 6 Per cent 1669 2873 4083 4169 4061
900 900 900
4009
825
3136
875
3936 3905 3740 0 . 8 Per cenl 3578 3743 4337 4453 4198
825 825 825
2992 2805 2746
850 850 825
900 850 825 825 825
3488
850
3876 3532 3465
850 850 850
4093
825
3287
825
4090 3945 3661 1 .O Per cent 4144 4404 4626 4568 4283
825 825 800
3171 3123 2903
825 825 825
850 800 800 800 800
3886
800
3871 3905 3766
800 800 800
4151
775
4131
775
3422
775
3809 4012
725 750
3058 3349
750 775
The isolation of pure compounds of dithiofuroic acid is extremely difficult, so that we cannot be certain of having worked with chemically pure compounds in these experiments with the thio derivatives of furfural. I n fact, the data relative to the physical properties of pure dithiofuroic acid found in the literature are very meager and it is extremely doubtful that pure dithiofuroic acid or its salts have been prepared by any of the workers who have thus far reported the preparation of these compounds. As can be readily seen, very few of the possible furfural derivatives likely to have accelerating action have been studied. It is highly probable that there are a large number of such compounds with varying degrees of accelerating activity. Since furfural is rapidly reaching a position among the cheap raw materials for organic synthesis, it is hoped that ultimately many accelerators will be prepared from it. ilt the present time hydrofuramide can be produced a t a price one-fourth to one-third the price of accelerators of the same general type, while dithiofuroic acid can be produced for substantially less than the price at which ultra-accelerators are now listed. Naturally, the writers will endeavor to produce and study many of these derivatives, but the field is so extensive and so full of interesting possibilities that undoubtedly it will attract many workers in the near future. Rubber Block Pavement Successful in Boston-Tests on rubber block pavement, laid one and one-half years ago a t the entrance t o the Boston City Hospital, have shown marked advantages. In addition to having worn but little, the pavement has the advantage that snow and ice do not collect on i t as on other types of pavement, thus doing away with slipperiness. The blocks are also almost noiseless and vibrationless. They are made largely of reclaimed rubber, and are laid in plastic sand and cement directly on the street foundation.
