NGER TIRES
FLEX LIFE
Relationship of Rayon Tire Cord Dip Pickup and Cord Adhesion R. T . MURPHY, L. M. BAKER, CiND R. REINHAHDT, JK. The Mansfield Tire & Rubber CompnrLy, Mansjield, Ohio Treatment of rayon tire cord with adhesive or dip solutions of the reclaimed rubber dispersion, GR-S Type I11 latex, casein type has been studied to determine the relationship among the quantity of adhesive solids deposited, or dip pickup, single cord adhesion, and tire life under high flex running conditions. Two series of tire tests have shown that tire performance can be improved when lower amounts of dip solids are deposited even though single cord adhesion values are reduced.
facturing operations. The tires were run at 25 miles per hour under test wheel conditions of rated load and with inflation pressure adjusted t o produce 20y0 deflection. Adhesion tests were made at room temperature with the single cord H test as described by Lyons, Selson, and Conrad ( 2 ) and adhesion stocks of the following composition: First Test No. 3 srnoked sheets GR-S Whole tire and peel reclaim
Z,P.C.
Philblack A Zinc oxide B.L.E. Ratty acid Asphalt Process oil Santocure Barak Sulfur
AYON tire cord must have upon it a n adhesive film in order t o establish a bond between the cord and the tire body stoclrs. Gillman and Thoman (I) have shown that, with an adhesive of a given composition, adhesion between cord and rubber is a function of solids pickup, or that adhesion increases as the thickness of the adhesive film increases. The same work showed that increasing the concentration of solids in the dippirig bath is a n effective way t o bring about a n increase in solids pickup; and that other factors, such as cord tension through the dipping bath, speed of processing, and viscosity of the dip bath also affect dip pickup. This work with reclaim dispersion, GR-S latex, casein systems has been undertaken t o determine how variations in dip-solids pickup and the resulting changes in single cord adhesion affect the flex life of rayon cord in passenger tyres. It has been found that there is a marked relationship among adhesion, dip deposit, and tire life. This relationship is discussed in detail below.
Table I list3 information on the materials used in this work I n the first test described below, the rayon cord fabric was dipped by use of a Waldron unit, then coated on a separate, 2calender train. In the second test, the fabric was dipped, dried, and calendered with the Waldron unit and a &roll calender in tandem. Rtodern factory-size equipment for preparing caseinate solutions and blending and bullring of dip solutions was used throughout.
2
I 1 7 8
1 0.5 2.75
186.25
Second Test No. 1 smoked sheetr E.P.C.
S.R.F.
Zinc oxide B.L.E. Stabilite Prtraflux Pine t a r Staybelite resin F a t t y acid Barak Benzothiazyl disulfide Rulfnr
100 20
30 18 1 0.4 5 1.3 5.5 2 0.5 0.65 2.6
181.95
Wd = weight of dipped roll of fabric M d = moisture content of dipped roll of fabric 1Vd (dry) = dry weight of dipped roll of fabric TVu (‘dry) = dry weight of undipped roll of fabric D = weight of dip solids used V = volume of dip solution used in gallons Du = weight of d i p solution per gallon Ts = total solids concentration of dip solution
TESTING PROCEDI-RE
Calendered fabric wa5 built into 6.50, 16 four ply paseriger tires and evaluated on a 48-inch diameter indoor test wheel. In each test, the tires were made as nearly identical as possible bv use of a blend of stoclis and very careful supervision during all manu-
Wd (dry) = R’d - (Il’d X .lid) D =
V X D u X T s
Wu (dry)
T ~ B LI.E ~ I I T E R I A L ~ 1650 denier/2 ply 0 0276 inch Approx. 80 s/1. 2 picks per inch
Ingredients for drp baths Water dispersions of whole tire reclaiin GR-S latex Type 111 Argentine 30-mesh casein solubilwed w i t h horax -
13
The jaws used for pulling the H test pieces were the slottedledge type designed by C. E. Carlson, research director, Pennsylvania Rubber Company. Dip pickup was determined as the amount in per cent by weight of dry-dip solids deposited upon the original dry, undipped fabric, or dry-dipped weight of fabric minus dry-undipped weight divided by dry-undipped weight. These weights mere determined as follows :
MATERIALS AND EQUIPhfENT
Rayon cord fabric Cord construction Gage Filhng
42 16 84 8
I
=
W d (dry)
-D
This method of determining dip pickup does not take account of the very small per cent of dip solids left in the drying oven Another method of determining the total amount of dip solids actually deposited on the fabric includes calculation of dry undipped fabric weight from the weight and moisture content of the undipped fabric. This second method was discarded in favor of the method used because it was believed that the amount of drydip solids used could be determined more accurately, even dis-
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December 1948
2293
regarding quantities left in the drying oven, than could the moisture content of the undipped fabric due t o uneven moisture distribution. DESCRIPTION O F TESTS
Two separate tests were completed. The first test included the four dip formulas shown in Table I1 and was designed t o evaluate four basic versions of the reclaim, GR-8, casein type of adhesive. Variations in reclaim-GR-S ratios, casein content, total solidi concentrations, and types of reclaim dispersion were involved. I n one case, vulcanizing ingredients were added. The results were analyzed from several viewpoints, and it was observed that the best tire performance accompanied the lowest values of dip pickup and single cord adhesion. Since this tendency appeared to be in opposition t o some generally accepted beliefs, it was decided to investigate further. As a result, the second test was designed to include the three formulas shown in Table 111. Formula I1 from the first test was arbitrarily chosen and varied as follows: Formula V in the second test duplicated Formula I1 in the first test, except that the total solids concentration was reduced from 25 t o 18%. The added casein in Formula V was then eliminated to give Formula VI, a potentially lower adhesion mixture. Formula V was also diluted to one half its original total solids concentration to give Formula VI1 in order to reduce both single cord adhesion and dip pickup. TEST RESULTS
In addition t o test results shown in Tables I1 and 111, there were no significant differences in running temperatures among all tires tested. All iailures were of the same general type. Failures
TESTFORMULAS AND RESULTSO TABLE 11. FIRST Formula I Formula I1 Formula I11 Formula I V 50 25 25 15 75 75 85 50 Soap disp. Approx. Approx. Approx. 19%. containing 6.5%. 13,%. casein in casein in vulcanizing casein in dispersion dispersion ingredients dispersion
Ingredients, D r y Basis GR-S latex type I11 Reclaim dispersion
Casein added (as Yo of total finished dip solids) Total casein (as Q of total finished odip solids) Total solids concn. of finished d i p % H test adhesion, pounds Dip pickup, 7 0
15
6
8
Figure 1. Various Stages in the Development of Pick Cutting
were fatigue breaks in cord fabric in shoulder and side-wall area, the region of greatest flexing. A careful examination of failed cords from the tires showed evidence of fatigue particularly at the point where the filling yarn crossed the warp cords. This condition is commonly referred t o as pick cutting. Figure 1 shows various stages in the development of this type of failure. I n the cord on the left failure is almost complete, in the middle cord one ply has failed, and in the cord on the right the rupture of individual filaments has just begun. All failures shown are where the filling yarn crossed the warp cords. Cord fatigue and separation between ply stocks occurred together in some tires. I n other tires fatigue breaks occurred with no evidence of ply separation. This would indicate that cord fatigue was the primary failure in all tires. DISCUSSION OF DATA
I n spite of the variation among the formulas in the f i s t test, the outstanding observation was the tendency for tire life under high flex running conditions t o increase as the amount of dipsolids deposit decreased along with single cord adhesion values.
5.5
20
15
8
10
18.6 8.5 8 8
25 8.3 9.7
20 7.2 7.3
20 7.0 6.5
Relative Test Wheel Mileage as % of Control Value eoond tire 'hird tire
A 108 92
103.5 45 70.5 73
120.5 93.5
121.5 97.5
ioo io7 l&:5 ontrol value) a Carcass compound used contained approximately 65 parts GR-S, 20 parts crude rubber, 30 parts whole tire reclaim. TABLE
111.
SECOND
TESTF O R V E L A S
Ingredients, D r y Basis Formula V GR-S latex type I11 25 Reclaim dispersion (containing 75 approx. 13% casein) Casein added (as % of total finished dip solids) 6 Total casein (as % of total finished dip solids) 15 Total solids concn. of finished dip, 18 % 9.9 H test adhesion, pounds
ANI)
RDSULTS~
Formula VI Formula VI1 25 25
75 0
6
9
15
17
4.0
Relative Test Wheel Mileage 8 s % of Control Value 88 79 First tire 118 119 Second tire 99 103 Average A 100% crude rubber carcass stock was used in this test. @
75
B Figure 2.
Microscopic Examinations of Dipped Calendered Cords
and
9
8.3
135 169 152
Figure 3. Single Warp Cord with Filling Yarn Removed Showing the condition Sketched in Figure 2
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Figure 4.
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
Deposit of Dip Solids Readily Visible under a Microscope
Vol. 40, No. 12
T o approach an explanation of the effect of amount of dip deposit on the fatigue resistance of rayon cords, tire t,ests were performed which showed that failure of the warp cords a t the filling yarn was evident in the high flex areas of the t,ires. Since the presence of the filling yarn produces a potential point of failure when it crosses the cord, it was undertaken t o determine how the filling yarn affects the deposit of dip solids a t t h a t spot. Microscopic examinations of dipped and calendered cords havu shown that during dipping two things happen where the filling yarn crosses and is in contact with the warp cord. First, there is no deposit of dip solids between the filling yarn and the cord; second, there is a n excess of dip solids near and on the filling yarn. Figure 2 shows sketches of these conditions. Figure 2, A , represenk a longitudinal cross section of a warp cord and transverse cross sections of filling yarns t,o illustrate the pileup of dip solids a t the filling yarns and Figure 2, B , represents the exterior appearance of a warp cord with one of the filling yarns removed. I n Figure 2, although the scale of filling yarn size to cord size is approximately correct, the interval between filling yarns has been reduced. Figure 3 is a photograph of a single warp cord with filling yarn removed showing the condition sketched in Figure 2, A . During the processing of ~vovencord fabric through a Waldrori unit, there is an opportunity for considerable runback of dip solution over the warp cords, particularly at t.he squeezing operation. This runback is blocked between the cords and on the surface of the cord by the filling yarn and a build-up of dip solids occurs as the solution is concentrated a t and on the filling yarn. Also, even after squcczing an excess of solution remains near the filling yarn and results in a deposit, of dip solids readily visible under a microscope.
Figure 5 . Difference in Deposit at the Filling Yarn when 9% Total Solids Solution is Used
I n the second test, three variations of the same basic recipe showed that flex life of cords in tires was not changed significantly by a change in casein content and a minor change in total solids concentration. On the other hand, when the basic recipe with added casein nab diluted t o half its original total solids concentration, a very sharp increasc in fatigue resistance was noted. Since only enough rayon fabric was treated in the second test to allow the building of test tires, no attempt was made t o determine dip pickup values a t the time of processing. It is assumed, however, t h a t no pronounced difference in dip pickup existed when Formulas V and V1 were used and that a definite reduction in dip pickup occurred when Formula VII, the 970 solids mixture, was used. This is in line with the conclusions of Gillman and Thoman (1) who show that dip pickup decreases as the total solids concentration of the dip bath decreases. The principal assumption, thcn, is that in the second test, dip pickup values for Formulas V and VI were essentially the same and that this value for Formula VI1 was considerably lower. This is confirmed by the Ion-er adhesion value obtained with Formula VII. Based on this assumption and the data listed in Table 111,the following conclusion has been reached: When the adhesive film is derived from a dip solution of the reclaim dispersion, GR-S latex, casein type described under Formulas V and VII, it appears that flex life of woven rayon cord fabric in passenger tires is improved by lower pickup of dip solids, even though single cord adhesion values are reduced.
Figure 6.
Dip Deposits on the Filling Yarns
Figure 4 shows this condition when an 18% total solids solutiori such as Formula V is used. For comparison, Figure 6 shoavs the difference in deposit a t the filling yarn when a 9% total solids solution such as Formula VI1 is used. I n Figure 6, dip deposits on the filling yarns thcmselvcs are shown with the results of dipping in an 18% solution on the left and in a 9% solution on the right. The filling yarns were removed from the warp cords before being photographed. It is known t h a t cord-dip solutions of the type described produce stiff, hard dried films. The presence of an excess of such a film in contact with the filaments of a rayon tire cord is believed to be one of the causes of the ultimate failure of the cord under high flex conditions, particularly when excess deposits flank a spot where there is no deposit and produce a hinge point. A reduction in dip solids reduces the over-all deposit on the cords and results in longer flex life in the cords themselves.
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CONCLUSIONS
ACKNOWLEDGMENT
The contention is, then, t h a t with reclaim dispersion, GR-S latex, casein dip solutions, the best flex life in woven rayon passenger tires is obtained with lower amounts of dip pickup. High single cord adhesion values do not guarantee good tire performance; therefore, less emphasis should be placed on such tests.
The authors wish to express their appreciation t o It. Schmahl who drew the figures used in illustrations.
SUMMARY
(2) Lyons, W. J., Nelson, M. L., and Conrad, C. M., India Rubhe7 World, 114, 213-17, 219 (1946).
LITERATURE CITED
(1) Gillman, H. H., and Thoman, R., IND. ENG.CHEM.,40, 1237 (1948).
The tests described herein show t h a t in woven rayon passenger tires, tire performance is improved when the quantity of dip Pickup is reduced, even though there is a sacrifice in adhesion values.
RECEIVEDSeptember 23, 1947. Piesented before t h e Division of Rubbei Chemistry at the 112th hleeting of the A,IERICAV CHE,~IICAL SOCIETY, N~~ Yo&, N. Y .
Diolefins in Alkylation Feedstocks J
Conversion to Mono-oleJins by Selective Hydrogenation JOHN ANDEKSON, S. H. IMCALLISTER, E. L. DERR, AND W. H. PETERSON Shell Development Company, Emeryville, Calif.
During the critical wartime shortage of light olefins for alkylate gasoline manufacture, means of extending the supply of butylenes and amylenes were sought and possible processes for purification of unsuitable refinery fractions were investigated. Materials contaminated with diolefins were available to some extent, and a vapor phase process for converting the diolefins i n such materials to monoolefins by selective hydrogenation was devised. The supported nickel sulfide catalysts employed in the hydrogenation process have a remarkable degree of selectivity i n t h a t they are active for hydrogenation of diolefins to monoolefins but relatively inactive for the hydrogenation of mono-olefins to paraffins in the temperature range of 200 to 300 'C., even i n the presence of a large excess of hydrogen. Butene and pentene fractions having diolefin contents rendering them unsuitable for isoparaffin alkylation were converted b y hydrogenation over nickel sulfide catalysts
to fractions giving excellent alkylation results. The hydrogenated materials had mono-olefin contents corresponding to the combined concentrations of diolefins and mono-olefins originally present and alkylate yields were improved by amounts depending on the increase in monoolefins in the feedstocks. Investigation was directed primarily to continuous vapor phase operation under conditions readily obtainable i n existing hydrogenation units of the types used for hydrogenating catalytically cracked gasolines or for converting butene dimers to iso-octanes. The nickel sulfide catalyst employed in most of the work was prepared from a commercially available nickel carbonate-alumina by merely treating with hydrogen sulfide a t 400" C. This material proved to have a life of over 1000 hours when treating a Ci fraction containing 23 mole 7 0 butadiene, and, after losing activity, i t was again rendered active by burning and resulfiding.
I
Although examples of the partial hydrogenation of diolefins 0 1 acetylenes t o mono-olefins i n the presence of active mctal hydrogenation catalysts are well known in the literature (?), the conversion of the poly unsaturated materials t o the corresponding mono-olefins by vapor phase hydrogenation is rendered difficult by the tendency of the mono-olefin first formed to add more hydrogen and become completely saturated. This difficulty is enhanced when the diolefin undergoing hydrogenation is present, as in alkylation feedstocks, along with a high concentration of mono-olefin which can compete for the catalyst surface and the hydrogen. Nevertheless, in the preliminary stages of the present investigation i t was found possible by limiting the proportion of hydrogen, with nickel metal catalysts, to remove substantially all diolefins from C4 and Cs fractions containing initially 4 t o 60% of diolefins without taking a n accompanying net loss in mono-olefin content. Figures 1 and 2 show typical vapor phase hydrogenation results obtained with a nickel catalyst. It will be seen t h a t a hydrogen to diolefin mole ratio of around 2 t o 1 was required for complete diolefin removal and that the products using this ratio had mono-olefin contents similar t o those of the feeds. With a nickel tungsten sulfide hydrogenation catalyst i t was possible t o adjust conditions, even with a severalfold excess of
N THE alkylation of isobutane (2-methylpropane) with olefins
for the production of highly branched paraffins (1, %), the life of the sulfuric acid or hydrogen fluoride catalyst is usually limited through dilution with soluble hydrocarbon by-products. When pure feedstocks are employed, these by-products are apparently formed b y hydropolymerization of the olefin (3,6) urhich occurs t o a small extent as a competing reaction with alkylation. When diolefin impurities are present in the charging stocks, diolefin polymers and diolefin-mono-olefin copolymers also dissolve in the acid catalyst, curtailing its life still further. Concentrations of diolefins above about 2 t o 3% of the olefin reactants are usually sufficient t o render the alkylation rconomically impractical because of high acid consumption. Removal of diolefins from olefin fractions can be accomplished by selective polymerization (6), but polymerization methods are not entirely satisfactory because of losses due t o accompanying mono-olefin polymerization. I n view of the need for a widely applicable process for removing diolefins from butylene (butene) and amylene (pentene) alkylation feedstocks and the possibility t h a t a suitable process might be based on hydrogenation, a search was undertaken for catalysts and conditions t h a t would allow selective hydrogenation of diolefins in the presence of monoolefins.
