Reaction of furfuraldehyde and pyrolysis oil tire scrap
United States Patent [1 1 Wakefield et al.  
 [4 1 Apr. 29, 1975 REACTION OF FURFURALDEHYDE AND PYROLYSIS OIL TIRE SCRAP Inventors: Lynn Burritt Wakefield; Durward Thomas Roberts, Jr.; Edward Leo Kay, all of Akron, Ohio Assignee: The Firestone Tire &amp; Rubber Company, Akron, Ohio Filed: Mar. 16, 1973 Appl. No.1 342,245  
 [56] References Cited UNITED STATES PATENTS 1,986,050 1/1935 Fairley 260/720 2,871,205 l/l959 Mankowich et al. 260/710 3,231,544 l/l966 Cotman et al. 260/67 A 3,809,680 5/1974 Wakefield 260/51 R Primary Examiner Murray Tillman Assistant Examiner.l. Ziegler [5 7] ABSTRACT The invention relates to a resinous rubber tackifier and stabilizer prepared by a catalyzed reaction of a furfuraldehyde and pyrolysis oil obtained by the destructive distillation of scrap tire vulcanizate.  
 2 Claims, No Drawings REACTION OF FURFURALDEHYDE AND PYROLYSIS OIL TIRE SCRAP The invention relates to the production of a solid resin by the reaction of formaldehyde or other aldehyde with oil obtained from the pyrolysis of vulcanized tire scrap, and the use of the resin as a tackifier and/or an antidegradant in the compounding of natural and synthetic rubbers.  
  Wakefield Ser. No. 236,438 filed Mar. 20, 1972, now US. Pat. No. 3,809,680 relates to hard resins prepared by reacting an aldehyde with the tire pyrolysis oil. Also, it has been known that some aromatic hydrocarbons, including m-xylene, anthracene and acenaphthene react with formaldehyde and other furfuraldehyde under the influence of a Friedel-Crafts catalyst to form alkylol-aromatic compounds which may be further reacted to produce resins used in the paint and rubber industries.  
  It has now been determined that resins obtained by the catalyzed reaction of an aldehyde on pyrolysis oil from vulcanized tire scrap, can be used as a useful rubber-compounding ingredient.  
  The composition of tire scrap varies considerably, the principal variation being in the elastomers and the mineral components of the scrap. There are several elastomers used widely in tires, namely, natural rubber, polyisoprene, polybutadiene, butadiene-styrene copolymer, polyisbutylene (Butyl), chlorinated Butyl. ethylene-propylene copolymers and terpolymers. The scrap to which industry refers as tire scrap is one in which the elastomer content is over about per cent by weight of the vulcanizate of such rubbers, and may or may not contain fabric. During the distillation of the scrap the mineral matter remains as a residue and. of course, some of the elastomer is charred, but a high percentage of oil distillate is obtained which is referred to herein as tire pyrolysis oil.  
  The distillate is derived from the elastomer present in the scrap and from oil that may be present in the scrap that is pyrolyzed. This oil may be aliphatic, aromatic or naphthenic. The composition of the distillate will vary with the temperature at which the pyrolysis is carried out and the dwell time of the scrap at the pyrolysis temperature. Usually the pyrolysis temperature will be between 1000 and 2500 F., but may be somewhat higher. The scrap is maintained at this temperature for .which has been compounded with the rubber before vulcanization will be found in the heavy fraction of the distillate. I  
  The Bureau of Mines Report of Investigation 7302 DESTRUCTIVE DISTILLATION OF SCRAP RUB- BERS, September l969, gives the following analysis of tire pyrolysis oils distilled at different temperatures:  
 TABLE 1 ANALYSIS OF DISTILLATE OIL There is a hig percentage of neutral oils in the distillate and a small amount of acids and bases. The analysis shows that there is a high percentage of aromatics present. The aldehyde treatment tends to condense the aromatics as well as react with the olefins and possibly with the naphthenes.  
  The Bureau of Mines Report also gives a Mass Spectrometric analysis of the distillate oil as follows:  
 TABLE ll MASS SPECTROMETRIC ANALYSIS OF OIL CALCINATION TEMPERATURE. C.  
 VOLUMEf/i Alkyl Bcnzcncs 19.0 20. Phenols 1.0 0.9 3-Ring Aromatics 1.5 2.4 Biphcnyl and Accnaphthcnc 6.1 8.5 Alkyl Naphthalcncs 8.9 29.7 lndencs 6.8 8. Styrene 2.0 4.5 Alkylstyrcncs and lndans l 1.2 5.8  
 Tire purolysis oils which have analyses of different components in about these ranges are representative of those which can be used in carrying out the invention.  
  Formaldehyde andthe other aldehydes react with the foregoing compounds.  
  Generally, oil recovered from pyrolysis of scrap rubber at higher temperatures will contain a higher content of aromatics thatn the oil obtained at lower temperatures. Such oils of higher aromatic content, are preferred for the preparation of resins of this invention.  
  lt is known that oil derived from the pryrolysis of different rubbers varies in its content of chemical which react with formaldehyde and other aldehydes to produce a solid resin. Five to fifty parts by weight of aldehyde may be used per parts of tire pyrolysis oil in the production of the resin. Commercially, tire pyrolysis oils which yield at least 50 per cent of such solid resin are preferred for use in the process of this invention.  
  The preferred aldehyde for commercial operations is formaldehyde or a formaldehyde generator such as paraformaldehyde, but other aliphatic, aromatic and heterocyclic aldehydes may be used, including acetaldehyde, propionaldehyde, benzaldehyde, tolualdehyde, furfural, etc.  
  Based on the foregoing. and considering the variation in the compositions of tire scraps and the effect of calcination temperature on the pyrolysis oil, the tire pyrolysis oil of this invention will preferably have the following analysis in percentages by volume:  
 TABLE III carried out in any suitable reaction vessel on either a batch or continuous basis.  
  The following is illustrative of the formaldehyde treatment of an oil obtained from vulcanized scrap tire PER CENT pyrolysis. The oil used is representative of what would be obtained in commercial production from a usual Alkyl Benzene -35 vulcanized tire scrap at any usual pyrolysis tempera- Phenols 0.1-5 34mg Ammmics ture, the pyrolysis bemg carried out in the substantial Biphenyl and Acenaphthene 5-25 absence of air. Alkyl Naphthalencs 5-35 10 133f: :jg PREPARATION OF PYROLYSIS on. Alkylsyrencs and Scrap pneumatic tires which were not useful for retreading were cut into pieces and then pyrolyzed in a although it is not intended to limit the invention to oils 5 hmzfimtal at temperaiurgs of 1200 140.0 i600 and 1800 F. The pyrolysis OliS generated during of this composition. However, the 0]] will contain a the pyrolyses were combined. The final blend produced total of at least per cent by volume of l alkyl benb blendin obtained over a ractical ran e of zenes, (2) alkyl naphthalenes, and (3) biphenyl and y g p py rolysis temperatures, may be assumed to be statistically acenaphthene. Any such pyrolysis Oli may be used in typical of large-volume production. carrying out the invention. Resin-precursor oils from Th e analysis of tire pyrolysis oll given in Table III is other sources may be added to the tire pyrolysis Oli typical and the analysis of the Oil obtained by the forewithout departing from the teaching of the invention.  
  going procedure should come within this analysis, and The reactions of formaldehyde with a wide variety of such typical oils used in the production of resins as here aliphatic and aromatic compounds are known. The mdescribed, should yield resms comparable to those devention relates to the reaction of formaldehyde or 25 scribed in Table N which follows. other aldehyde with a plurality of the pyrolysis Oli components to produce a valuable solid resin suitable for PRODUCTION OF TACKIFIER AND use as a rubber-compounding ingredient, the analysis ANTIDEGRADANT RESIN of which will vary from resin to resin, but the composition of the pyrolysis oil does not vary so much as to pro- The general procedure for preparing the resins of this duce a wide variance in the properties of the resins that invention was to charge a glass pressure bottle with the are obtained. pyrolysis oil and the aldehyde (usually paraformal- Commercially, a Friedel-Crafts catalyst may be predehyde but other aldehydes would be effective) and fiferred because it is known that it speeds alkylation renally the catalyst was added. The pressure bottle was actions. Catalysts which may be used advantageously sealed and rotated end-over-end in an 80 C. water include boron trifluoride complexes such as the alkyl bath for 16 to 23 hours. The pressure bottle was then ethers, hydrate, phenolate; anhydrous aluminum chloremoved, cooled to room temperature, opened, and the ride, zinc chloride, etc.; a protonic acid, e.g. sulfuric contents diluted with toluene. (Methylethyl ketone or acid, p-toluene-sulfonic acid, etc.; sulfurand phosother solvent may be used.) The diluted reaction mixphorous-bridging condensation catalysts including a ture was treated with an excess of solid dry sodium carchloride or oxychloride of sulfur, e.g. sulfur monoor bonate to neutralize the catalyst residues and the mixdichloride, thionyl chloride, sulfuryl chloride, etc. or of ture subjected to vacuum distillation. All material disphosphorous, e.g. phosphorous trichloride, phosphotilled up to 190 C. at 4 mm. pressure was discarded. rous pentachloride, phosphorous oxychloride, etc. The hot residue was poured into an aluminum foil cup The reactions of this invention catalyzed by the comand allowed to cool. In Table IV the yield of product mercial catalysts take place at a low temperature of the i expressed as a weight percentage of the complete order of -25 C. However, such reactions are slow and charge. The products were hard (H) to hard-brittle higher temperatures are preferred; for example, from (HB) in physical appearance. The results of a series of ambient temperatures to 250 C. The reactions may be runs are summarized in Table IV.  
 TABLE IV CONTROLS AND EXPERIMENTAL RESINS RUNS: l 2 3 4 5 6 7 8 9 10 ll l2 l3 l4 l5 OILS:  
  Dutrex 726 100 T00 Whole Pyrolysis Oil I00 I00 100 100 I00 100 I00 I00 I00 I00 I00 Volatile Fraction Non-Volatile Fraction 35 ALDEHYDES:  
  Paraformaldehyde 2O 2O 20 20 20 2O 20 2O 20 20 20 20 Furfuraldehyde 20 CATALYSTS:  
  BF Etheratc 5 5 5 5 82C], 5 SOC], 5 SO Cl, 5 PCI 5 5 PCI 5 OCl H150, 5 l0 p-Toluene sulfonic acid 10 0 5 P 0 and O,  
 TABLE IV Continued CONTROLS AND EXPERIMENTAL RESINS RUNS: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CONDITIONS AND RESULTS:  
 Time, Hrs. 22 22 22 16 16 22 23 23 16 23 Yield, 7: 35 41 51 49 58 53 49 63 58 49 58 Nature of Product v0 v0 v0 HB H H H H H HB HB HB H HB HB Runs 1 and 2 of the foregoing table were included as points of reference. Dutrex 726 is a processing oil of high aromatic content which is used widely in the rubber industry. As will be noted in Table IV, treatment of the Dutrex 726 oil according to the general procedure of our invention resulted in a viscous oil (VO) rather than a hard resin. This indicates that pyrolysis oil as herein defined is unique, and on treatment with an aldehyde yields a very different product from that produced from Dutrex 726 which was not suitable as a resin for rubber compounding.  
  Run No. 3 indicates that if the pyrolysis oil is stripped of the volatile fraction (material that distills below 190 C. at 4 mm. pressure), the amount of residue amounts to about 35 per cent of a viscous oil based on the whole pyrolysis oil. This product could not be used as a tackifier resin.  
  Runs Nos. 4 through 12 illustrate that sulfur chlorides and oxychlorides as well as phosphorous chlorides and oxychlorides, Friedel-Crafts catalyst (e.g. BF etherate), and also protonic acids (sulfuric and paratoluenesulfonic acids, etc.), in the amounts by weight given are effective catalysts for formation of resins. Different amounts of catalyst may be used in the resin reaction.  
  Run No. 13 shows that oxidation by blowing the whole pyrolysis oil with air, using phosphorous pentoxide as catalyst, gives a hard resin, and this may be used as a rubber tackifier. Other catalysts than phosphorous pentoxide may be used.  
  Run No. 15 was included to illustrate that the pyrolysis oil may be added incrementally (the low volatile oil first, and then the non-volatile fraction) to the reaction mixture to obtain good results. In this run a sample of tire pyrolysis oil from the blend described above was separated into two fractions by vacuum distillation. The volatile fraction comprised all material distilling up to a boiling point of 190 C. at 4 mm. pressure. It amounted to about two-thirds of the total charge. When freshly distilled it is a clear yellow liquid, and on standing turns dark brown. The residue, about onethird of the total, is a viscous black oil.  
  The volatile fraction, about 65 grams, was charged with parts of paraformaldehyde to a glass pressure bottle, 5 parts of BF;, etherate was added and the bottle was sealed and rotated end-over-end in an 80 C. water bath for 16 hours. The bottle was then removed, cooled to room temperature and opened. Then 35 grams of the distillation residue was added. The bottle was again sealed and agitated at 80 C. for an additional 7 hours. As will be noted in Table IV, the yield was 58 per cent of a hard-brittle (HB) resin. Comparing this with the yield obtained from the whole volatile fraction (Run No. 12) using the same catalyst, it is found that a substantially greater yield was obtained, indicating that incremental addition is commercially desirable. The light-oil increment added first might be larger or greater than per cent as, for example, anything over 30 or 40 or 50 per cent, or even per cent, more or less.  
  Run No. 14 is included to illustrate that other aldehydes are applicable, specifically furfuraldehyde. Formaldehyde or paraformaldehyde is less expensive and thus there is a commercial advantage in using either of them. Resins prepared with furfuraldehyde do have less tendency to stain and may be preferred on this basis.  
  This invention is not limited in scope by the general procedures described above. It should be obvious to one skilled in the art that the catalyst, aldehyde or pyrolysis oil may be added in increments to the reaction mixture. The process may be conducted in a batchwise manner or continuously. The temperature may be lowered and the reaction time extended, or the temperature increased and the reaction time lowered to produce useful tackifying resins without departing from the intent of our invention.  
  The tackifiers and stabilizers of this invention are useful additives in rubbers used in tires, mechanical goods and other rubber products.  
 RUBBER COMPOUNDS 1n the following table the different pyrolysis oils and catalysts used in producing resins are those described in Table IV under the Run numbers given in the first line of Table V. All resins were compounded at a 17 parts per hundred of rubber level.  
 &#34;&#34;Commcrcial resin: Piccopale 100.  
 &#34;Experimcntal Resins designated by Run Numbers in Table IV. &#34;&#39;Tcsted at 300 F., 1 Arc and 100 rpm.  
 &#34;&#34;TS Scorch time in minutes.  
 &#34;TC() Time to optimum cure in minutes.  
  l (f) WX 100 =Cure Rate Index.  
 two compounded rubbers to stock together during fabrication and prior to vulcanization or curing.  
  Green strength&#34; is also an important factor during the manufacture of rubber articles (tires, mechanical goods, etc.); it is a measure of the uncured compounds ability to retain its geometric shape.  
  As shown by the data summarized in Table VI, the experimental resins impart tack and green strength values equivalent to or slightly better than a commercial resin (designated control resin in the Table).  
  Resin A was prepared by the general procedure described previously using BF etherate as a catalyst. Resin B was also prepared by the general procedure except the resin was heated only 3 hours under pressure hundred (phr) ofa commmercial resin (Piccopale 100) at C, rather th 16 h TABLE VI HYDROCARBON RESINS FROM PYROLYSIS OIL RECIPE: SBR/NR/Black/Oil/ZnO/Stearic Acid/S/Accelerator plus l7 phr of resin as indicated.  
 as a control, and in the test runs 17 phr of the experimental resins identified in the table by run numbers which refer back to Table IV. The base formula consisted of a commercial styrene-butadiene rubber plus some natural rubber and the usual amounts of carbon black, zinc oxide, stearic acid, sulfur and accelerator. Runs Nos. 2 through 6 of Table V indicate that the experimental resins imparted less scorch resistance to the rubber compounds than the control referred to in Run No. l and the cure rates were faster. Therefore, the time to optimal cure was in all cases less than that for the control. The faster cure rates of the experimental formulations are also indicated by the cure-rate indices; the higher the number the faster the cure rate. A higher cure-rate index is desirable from a commercial standpoint, since rubber compounds can be produced faster; thus realizing a lower unit cost.  
  Test data were not run on all of the examples identitied in Table V, but only illustrative samples were selected, and the results obtained with these are representative of what may be obtained with any of the other samples identified in Table IV.  
  The resins of this invention impart tack and green strength to rubber compounds with results comparable to commercially available resins.  
  Tack or more specifically building tack is a desirable property which some synthetic elastomers lack. Simply stated, tack is a measurement of the ability of The wind-up tack values and lnstron green stressstrain data as well as lnstron green stress degradation data on the experimental resins are all higher than on the control, using a commercial resin. Similar results would be obtained with the other experimental resins listed in Table IV.  
  In addition to the faster cure rates imparted to rubber compounds by the resins of this invention, we have unexpectedly discovered that the resins also impart antioxidant activity as indicated in Table VII which follows:  
 lized the Mooney viscosity of the polymer even after 8 days oven aging in a forced-air oven such as used in running standard laboratory stabilization tests. In contrast, the polymer containing no additive was completely gelled after 4 days aging. It is therefore completely useless from a commercial standpoint. It will be noted that the experimental resins gave Mooney viscosity retention values better than for the commercial antidegradent.  
 We claim:  
 I acid, p-toluene-sulfonic acid, the sulfurand phosphorl. A solid rubber tackifier or stabilizer resin which is the reaction product of 5 to 50 parts by weight of furfuraldehyde and 100 parts by weight of tire pyrolysis oil obtained by distillation of vulcanized tire scrap at a temperature in the range of l000 to 2500 F. which oil has the following analysis (volume percent):  
  PER CENT Alkyl Benzcnes -25 Phenols 0. l-5 3-Ring Aromatics O.l-5 Bi hcnyl and Accnanpthcnc 5-25 Alfiyl Naphthalcncs 5-35 lndcncs 1-20 Styrcnc l-l 5 Alkylstyrcncs and lndans l-25.  
 ous-bridging condensation type catalysts and Friedel- Crafts type catalysts, which oil has the following analysis (volume percent):  
 PER CENT Alkyl Benzenes l5-25 Phenols 0. l-5 3-Ring Aromatics 0.l-5 Biphcnyl and Acenaphthene 5-25 Alkyl Naphthalenes 5-35 lndcncs l-20 Styrene 1-15 Alkylstyrenes and lndans 1-25.