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The benefits from a partnership between the recycling specialist and tire maker.

As the rubber industry addresses the environmental and resource recovery goals of the nineties and all of the ramifications, we believe there is a real and growing need for a "new partnership" between the tire manufacturer and those in our industry who have proven experience and reputation for the reclamation of rubber waste in high volume by proven state of the art technology capable of achieving high performance SPC standards in the solution to these problems.

Over these past ten years, we have seen some significant new reclamation processing technology come on line that provides unique capabilities for the production of very fine powdered rubber, with extremely high quality, uniformity, exacting particulate specifications, coupled with cost effective re-incorporation performance results.

We believe this provides the user with very real opportunities for success and therefore a very genuine reason for close cooperation between those who know best the demands of their products and manufacturing needs and those who by their very survival and continuing success and growth in waste reclamation are best equipped to ensure the likely success of the waste recovery targeted objectives.

Having served this industry in "reclamation" and resource recovery for many years, I truly believe we are entering a new era for highly productive results from such a cooperative partnership.

Having said that, how can we proceed to build this "new partnership" for our mutual and national good, at an acceptable pace with progressive confidence in the results and without providing to yourself and your customer an unacceptable choice.

I believe I can best illustrate how this can be accomplished by reciting an actual case history, without identifying the customer, of a partnership project which commenced over three years ago and which represents a true success story where everyone wins.

It started with an idea by our company that seemed worthy of some initial technical investigation, upon which a paper was presented, and as a result a trial evaluation was made in a pilot production run by the client company.

What followed was an orderly progression product by product, type by type, plant by plant (by the client), until a solid basis for full scale introduction of this material into the product mix was launched in 1988.

In order for this program to work, while the client plant users of this material were doing their job, our team was setting up all of the necessary mechanics at each waste generating production site to handle, accumulate, transport and process this material to the required specification. Often this required changes in containers and special handling arrangements.

Meanwhile back at our factory the processing refinements and equipment revisions necessary to insure quality performance were being proven out and our quality assurance and process reproducibility trials were going forward to formalize with our customer the specifications and certifications that were required to insure the high confidence in this material's uniformity.

Together we had arrived at an exact per "batch amount" to be pre-measured and placed in low melt bags so the material's introduction into the plant's mix cycle was simple and thereby greatly reduced their packaging discard waste as well.

Finally we were ready to formalize our just-in-time delivery system of the processed waste materials to the user plants to meet their required inventory management conditions; the timely collection of generated waste from all customer plants in the United States and Canada; and the necessary factory processing and the just-in-time delivery to the user plants through the United States and Canada was commenced.

Now in its third year, this program has seen this previously categorized factory waste, utilized in 28 million tires that represent over 4.8 billion road miles without a documented road failure attributable to this material compound change. During this period, we have never missed a delivery/supply date, never had a rejected lot, and by actual SPC analysis over 2,400 random product samples have provided a 99.6% reproducibility results, thus a very high quality mix ingredient from waste reclamation has been sucessfully achieved.

What has this customer gained from this partnership? Savings in materials cost estimated at an average per passenger/light truck tire of $.10 each, or an estimated savings in compound ingredient costs to date of $2.8 million.

Has this resulted in a "product quality" reduction? On the contrary. In-field user/warranty results have been maintained or slightly improved and in-plant factory rejects have actually been reduced by the reduction of a random failure due to blisters caused in product fabrication.

Finally, the "waste stream/landfill" scrap tonnage of this non-biodegradable waste from this customer's plants has been reduced by 3,000 tons annually, at a plant savings in waste removal costs over these past three years of $315,000.

Thus this tire company has realized substantial savings and society has benefitted by the elimination of this waste stream from the landfill. The final product owner, you and I, have benefitted too by this shared cost benefit in tire manufactured costs.

At the processing plant new jobs have been created and a pride in accomplishment as a team member with the customer is shared by all of the people. At many of the waste generation sites, handicapped agency workers have been utilized in sorting and handling these materials prior to transport to our facility.

This "case history" typifies the gains that can be realized from this new partnership relationship in the 90s and we are confident that by working together many more such success stories can and will result.

What follows is a technical analysis of the potential for more such success stories utilizing waste reclamation powdered rubber materials in tire construction in the 90s without degrading performance and with significant cost incentives for each success.

Finely ground rubber

We will focus on the thrust of a recent study which suggests that along with all the other options available for dealing with the tire disposal problem, we do in fact have a definitive potential and a very good reason for the tire industry to consider increasing the amount of tire recovered material usage in new tire manufacturing.

For the purposes of this article, finely ground rubber is tire material ground to a particle size of 60 mesh or smaller, wherein at least 70% of the normal distribution of particles is smaller than 80 mesh. Such materials are ground by existing technologies. Table 1 indicates by tire type the components in which such finely ground rubber will work. Table 2 indicates the approximate component weights as a portion of the tire.
Table 1- tire components in which a fine
particle size ground rubber can be used
 Passenger/farm/ Medium truck/
 light truck off-the-road
 Bias Radial Bias Radial
Innerliner Yes Yes Yes Yes
Plycoat Yes Yes Yes Yes
Bead insul. No No No No
Chafer Yes No Yes No
Apex Yes No Yes No
Coverstrip No No
Black sidewall Yes No Yes No
White sidewall No No
Belt Yes No Yes No
Treadcap Yes Yes Yes No
Undertread Yes No Yes No
Table 2 - typical tire component weights
 Passenger Truck
 tire, % tire, %
 Cap 29 20
 Base or undertread 6 14
Carcass 8.5 18
Liner 8.5 8
Black sidewall 11 9
Bead insulation 1 1
Chafer/apex 8 1
Belt 7 1.5
Total 79 72.5
Reinforcing components 21 27.5
 100% 100%
Average tire weight 20 Pounds 100.0 Pounds

Tables 3 and 4 show at a 5% usage level, the pounds of finely ground rubber per passenger and/or truck tire. Tables 5 and 6 show the calculated usage of finely ground rubber in passenger and truck tires at a 5% usage level.
Table 3 - passenger tire usage of finely ground rubber at 5%
Component % % Ground Bias Radial
Tread 29 5% 1.45 1.45
Undertread 6 5% - -
Carcass 8.5 5% .43 .43
Liner 8.5 5% .43 .43
Black sidewall 11 5% .55 -
Bead insulation 1 - - -
Chafer/apex 8 5% .40 -
Belt 7 - - -
 3.26% 2.31%
Tire weight 20 20
Pounds ground rubber/tire .65 Pound .462 Pound
Table 4 - truck tire usage of finely ground rubber at 5% level
Component % % Ground Bias % scrap Radial
 rubber ground
 Cap 20 5% 1.0% 1.00
 Base 14 5% 0.7% 0.70
Carcass 18 5% 0.9% 0.9
Liner 8 5% 0.4% 0.4
BSW 9 5% 0.46% -
Bead insulation 1 - - -
Chafer/apex 1 5% 0.05% -
Beit 1.5 -
 3.51 % of 3.0% of radi-
 bias truck al truck tire
 tire wt. wt. could be
 could be ground
 ground scrap.
 scrap. 65
Tire weight - approx. 65 1.95 lbs.
Pounds ground rubber/tire 2.28 lbs.
Table 5 - potential consumption of finely
ground rubber in tires at 5% level
 Passenger production
 205.8 million
 Units Poundsltire Potential
Radial usage. lbs.
 95% of units 195.5 mil. .462 90 mil.
 5% of units 10.3 mil. .65 6.7 mil.
Total potential usage 96.7 mil.
Table 6 - potential consumption of finely
ground rubber in tires at 5% level
 Truck tire production 42 million units
 (a rage 65 pounds/tire)
 Units Pound/tire Potential
Radial usage, lbs.
 50% 21 Million 1.95 41 Million
 50% 21 Million 2.20 47.9 Million
Total production 88.9 Million

As can be seen, the total recycled finely ground rubber at only 5% level will require 185 million pounds of such materials annually, and our work suggests that this amount can readily be accomplished with even higher percentages possible as confidence in these results is achieved.

Most important to your consideration are the advantages this can provide in cost savings and in actual processing cost improvements, or if you prefer in permitting you to utilize these savings to allow the addition of higher quality revision to your product by using these cost savings to offset such other costs as may be necessary.

Let's take a look at the economic impact of using these recycled materials in your product manufacturing costs.

We begin by looking at the two major types and two major categories of tire manufacture and as the charts suggest, we have selected certain elements of the tire construction to support our analysis, conclusion and recommendations.

These pounds of finely ground rubber usage would result in a potential annual savings to the passenger tire manufacturer ranging form $20-$38 million, and to the truck tire manufacturer $22-$43 million, at usage levels of 5% and materials costs based on $20/barrel oil. Usage levels at a higher percentage combined with increased oil prices could result in even greater industry savings and benefits (table 7 ).


Certainly savings potentials of this magnitude are worthy of a concerted effort on the part of the technologists and the management in the tire industry.

In these times of escalating materials costs and tire disposal solution seeking, it is both timely and appropriate to realize that these results provide the potential for entry and cost savings and for the recovery of from 15-30 million tires per year for reuse by the tire manufacturers as an appropriate effort toward the solution of the nation's tire disposal problem.

To further substantiate the feasibility of using ground rubber in tires, three specific compounding examples are included to show the effects of finely ground rubber on tire compound properties. These examples are:

* A passenger tire tread containing 5 and 10 phr of finely ground rubber .

* An evaluation of a fine particle cryogenically ground rubber in truck treads done with highway testing (84,000 miles).

* A laboratory evaluation of cryogenically ground butyl and butyl reclaim in tire innerliners.

Passenger tire tread

Finely ground rubber was evaluated in a typical passenger tire tread at 5 and 10 phr. The formulation was 70/30/SBR/PBD blend. Table 9 shows the properties found for the compounds.
Table 9 - rheometer results
Control - no ground rubber Finely ground rubber
 5% 10%
Cure time - min. 21.87 22.00 22.04
Scorch time - min. 9.00 8.29 8.96
Max. torque - lb. 49.19 48.10 46.19

The physical properties show the usual decline in tensile properties with hardness, modulus and heat generation being maintained. As a result, finely ground rubber is used in numerous tire applications.

One question that often arises is the effect of finely ground rubber on the cure rate of the compounds. Table 10 demonstrates the effects in the three compounds tested and show no harmful effect.
Table 10 - test program - butyl innerline
 Test compound
Mixer mastarbatch phr
Butyl HT 1066 80
RSS #1 20
N650 65
Mineral rubber 4
Phenolic resin 2
Steadc acid 2
Napthenic oil 8
Zinc oxide 3
Sulfur 0.5
MBTS 1.5
 Total 188.0
Test Control Ground rubber Butyl
compounds reclaim
 5% 10% 15% 10%
Masterbatch 188 178.60 169.20 159.80 -
60 mesh ground - 9.40 18.80 28.20 -
Butyl reclaim - - - - 18.80

Evaluation of cryogenically finely ground rubber in a

premium truck tread stock

An evaluation of a finely ground rubber was carried out in truck tire treads. A commercial precured tread compound was retreaded on new steel radial truck tires. In addition, the same precured tread compound was prepared adding 15 phr (6.32%) of the ground rubber. These were retreaded onto the same type of new casings. The tires were 1 1R24.5 Goodyear Unisteel Tires. The tires were measured for wear during the life of the test (84,000 miles). The results show that the compounds containing cryogenically finely ground rubber performed as well as the control, and experienced no performance failures.


The experimental tires containing 15 phr of a fine particle cryoground tire scrap completed the 31,998 mile testing without incident. The overall wear ratings on drive and trailer positions were statistically equal to the control tires.

After 31,998 miles on both drive positions and trailer positions, there was no evidence of irregular wear, groove cracking/cut growth or separation in either the cryoground tires or the controls.

Wear data are shown for drive tires at 82,248 miles and trailer tires at 84,214 miles. The experimental 1 tires on trailer position were significantly better than the control after 84,214 miles; both cryoground experimentals were equal to the control after 82,248 miles on drive positions. All tires were equal for tread cracking (slight) and uneven wear (moderate) at completion of test.

Cryogenically flnely ground butyl in tire innerliners

The innerliner of passenger and truck tires is one of the most expensive components of the tire. In addition, due to the inherent low permeability to air through the rubber compound, any air trapped during the mixing or processing may not escape during the curing and cause blisters. Cryogenically ground butyl rubber is effective in lowering the cost of butyl innerliners. It also provides a path for air to escape in the vulcanized state during curing and has no adverse effect on permeability in the cured state.

A laboratory evaluation (table 11) was made of a 60 mesh cryogenically ground butyl at 5, 10 and 15% by weight. A butyl reclaim was included for comparison.

Cost analysis

Some typical passenger and truck tire compounds were selected and a cost analysis performed to determine the cost savings that could be realized using finely ground rubber. Cost analyses were made for treads, carcasses and innerliners.

The finely ground rubber was priced at $.21/pound for the tread and carcass while the ground rubber added to the liner was priced at $.32/pound.

The costs were determined using list prices from chemicals as well as estimating the cost of compounds taking into account large volume purchases. This was done to give a realistic perspective on the true cost savings available to a major tire manufacturer. The results of these calculations are available upon request.

The cost savings found ranged from about $.005 cent per pound for the less expensive components of the passenger tires, to almost $.03 per pound for costly truck tire components like halobutyl innerliners.

The net effect taking the industry as a whole, is that if finely ground rubber were used in all applications where suggested at 5%, the net result would be a savings of about $.10/tire for passenger tires and $.55/tire for truck tires. This is summarized in table 7.


The principal purpose of this presentation has been to display proven results along with the potential benefits for using fine rubber powdered reclamation materials which reduce your compound/product costs and maintain your product performance while contributing to the national goals of increased recycling of non-biodegradable waste. The chances for success in a growing number of reclamation projects now underway suggests that the time has arrived for this "new partnership" in resource recovery/reclamation and the tire industry.
COPYRIGHT 1992 Lippincott & Peto, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
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Author:Smith, Fernley G.
Publication:Rubber World
Date:Sep 1, 1992
Previous Article:A recipe for customer satisfaction.
Next Article:Material recycling of RIM-polyurethanes.

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