Rubber Recycling: Emerging Markets and New ... - ACS Publications

Chapter 18

Rubber Recycling: Emerging Markets and New Technology Fernley G. Smith

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Emerging technology f o r the p r o d u c t i o n o f recycled rubber and a changing market environment more willing t o c o n s i d e r r e c y c l e d rubber as a v i a b l e rubber m a t e r i a l i n product design and applications, supported by acceptable performance and cost effective results, makes the n e a r l y 25% per year p r o j e c t e d growth r a t e a realistic outlook f o r the expanding rubber r e c y c l i n g i n d u s t r y .

Recycled thermoset rubber has been a standard m a t e r i a l of the rubber i n d u s t r y f o r many years. The e a r l y c a p a c i t y f o r the manufacture o f ground rubber and the p r o c e s s i n g t e c h n o l o g i e s grew out o f the r e c l a i m rubber plant needs for a uniform crumb rubber f o r d e v u l c a n i z a t i o n purposes. (1) Through the years, t h i s ambient temperature grinding technology has been improved and expanded from the o r i g i n a l 2mm t o .85mm c a p a c i t y t o the .60mm t o .425mm s i z e s now widely used i n the rubber i n d u s t r y . In the 80 s the f i n e r g r i n d i n g technologies emerged v i a cryogenic and wet g r i n d i n g systems t o generate from v u l c a n i z e d rubber waste, mesh s i z e s ranging from ,425mm t o .150mm and f i n e r . f

0097-6156/95/0609-0202$12.00/0 © 1995 American Chemical Society In Plastics, Rubber, and Paper Recycling; Rader, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


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Rubber Recycling: Emerging Markets and New Technology

Throughout these years o f t e c h n i c a l development and improvements, the i n d u s t r y remained relatively s t a b l e , with modest annual growth as niche a p p l i c a t i o n s for r e c y c l e d ground rubber were developed. By 1990 s a l e s t o t h i s market were estimated a t around 160 m i l l i o n pounds annually, produced by a r e l a t i v e l y small group o f processors with p r o c e s s i n g c a p a c i t y t o t a l i n g between 250 and 300 m i l l i o n pounds. Of t h i s annual s a l e s volume, approximately 65% was ambiently ground m a t e r i a l o f s i z e .60mm and coarser, with the remaining 35% a t .425mm and f i n e r . (2) This s h i f t t o f i n e r p a r t i c l e size i s continuing. Ground rubber has h i s t o r i c a l l y been dominated by a p l e n t i f u l supply o f t i r e b u f f i n g s as the raw m a t e r i a l of choice, and has been augmented based on f a c t o r y waste t o meet customer requirements. The p r i n c i p a l uses f o r ground rubber i n 1990 were: Pneumatic t i r e s F r i c t i o n materials-brake pads Molded rubber goods Bound rubber goods A t h l e t i c surfaces and playgrounds Rubber p l a s t i c compounds T i r e s / b i a s p l y and r e t r e a d stocks Tire innerliner Crack s e a l e r / a s p h a l t Asphalt rubber binder Over a t e n year p e r i o d from 1984 t o 1994, f o r t y eight states instituted regulatory scrap tire management l e g i s l a t i o n with economic i n c e n t i v e s t o do so, which has r e s u l t e d i n a scrap t i r e recycling infrastructure with a first stage size reduction c a p a c i t y capable o f producing 50mm to 125mm s i z e chips and a coarse 6-12mm rough crumb from scrap t i r e s . As o f 1994, there are over 150 such new s i z e r e d u c t i o n processors i n p l a c e capable o f i n i t i a l s i z e reduction of t i r e s . In a logical p r o g r e s s i o n , many o f these new processors are a c t i v e l y planning f u r t h e r p a r t i c l e s i z e reductions t o y i e l d 6.3mm and 2.00mm crumb and smaller as they can i d e n t i f y markets f o r t h i s additional p r o c e s s i n g investment. This s i g n i f i c a n t new investment i n p r o c e s s i n g c a p a b i l i t y w i l l u r g e n t l y seek markets f o r these m a t e r i a l s , t o improve the recovery value o f the processed scrap t i r e s . This p l e n t i f u l supply o f feedstock, t o supplement the exhausted supply of buffings, i s a timely development. Today, we see s e v e r a l emerging trends f o r new uses o f ground rubber. Foremost i s the use i n asphalt rubber i n roads. (Table I) t a b u l a t e s and

In Plastics, Rubber, and Paper Recycling; Rader, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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204

PLASTICS, RUBBER, AND PAPER RECYCLING

Table I. Selected Crumb Ruhbrr Modifier Terminology


Trnn Crumb Rubber Modifier (CRM)

A general term f o r scrap t i r e rubber that i s reduced i n size and i s used as a modifier i n asphalt paving materials.

Granulated

Cubical, uniformly shaped, cut crumb rubber p a r t i c l e s with a low surface which are generally produced by a granulator.

CRM

Granulator

Equipment that shears apart the scrap t i r e rubber, cutting the rubber with revolving s t e e l plates that pass a close tolerance, reducing the size o f the rubber to a crumb p a r t i c l e (generally 9.5 millimeter [3/8 inch to No. 10] sieve>

Ground Rubber CRM

I r r e g u l a r l y shaped torn crumb rubber p a r t i c l e s with a large surface area which are generally produced by a crackermill.

Micro M i l l

Process that further reduces the crumb rubber to a very fine ground p a r t i c l e , reducing the s i z e of the crumb rubber below a 425 micron (No. 40) sieve.

Rubber Aggregate

Crumb rubber modifier added to hot mix asphalt mixture using the dry process which r e t a i n s i t s physical shape and rigidity.

Asphalt Rubber (AR)

Asphalt cement modified with crumb rubber modifier.

Wet Process

Any method that blends crumb rubber modifier with the asphalt cement p r i o r to incorporating the binder i n the asphalt paving project.

Dry Process

Any method that mixes the crumb rubber modifier with the aggregate before the mixture i s charged with asphalt binder. This process only applies to hot mix asphalt production.

Rubber Modified Hot Mix Asphalt (RUMAC)

Hot mix asphalt mixtures which incorporate crumb rubber modifier p r i m a r i l y as rubber aggregate.


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d e f i n e s the key terms commonly used i n the a p p l i c a t i o n of ground crumb rubber i n highway asphalt paving.


A s p h a l t Rubber: Specifications

Processes

and R e l a t e d

Crumb

Rubber

Wet Process. The wet process (Figure 1) uses ground scrap t i r e rubber i n s i z e ranges from 2.4mm t o . 7mm. Through the use o f s p e c i a l equipment, the rubber is swollen i n the asphalt binder under the high temperatures and a g i t a t i o n o f the mix. After a s p e c i f i e d residence time, the l i q u i d rubber r e i n f o r c e d asphalt i s added t o the g r a v e l aggregate at the hot mix p l a n t and the r e s u l t i n g asphalt mix i s now ready f o r placement as paving. The l i q u i d asphalt rubber binder used i n asphalt paving i s a l s o widely used f o r s p r a y - a p p l i e d surface treatments, where i t becomes an e f f e c t i v e membrane f o r c o n t r o l l i n g adverse sub-base road c o n d i t i o n s . Dry p r o c e s s . The d r y process (Figure 1) use o f scrap t i r e rubber v a r i e s from the wet process i n that the rubber i s i n t r o d u c e d as a p a r t i a l replacement f o r g r a v e l aggregate i n the asphalt paving a p p l i c a t i o n . The d r y process, t h e r e f o r e , uses a "coarse g r a n u l a r " crumb m a t e r i a l with 6.3mm s i z e combined with a p o r t i o n of f i n e r ground crumb i n the 2mm t o .85mm range. Polymer M o d i f i e d process. This process i s based on the use o f v i r g i n polymers mixed with the a s p h a l t s to achieve improved performance. I t can be e f f e c t i v e l y modified by the p a r t i a l use o f .60mm t o .425mm ground scrap t i r e crumb rubber t o e f f e c t i v e l y r e p l a c e the polymers at a lower cost and acceptable performance. Continuous Blending process. This process f o r the production o f rubber i n asphalt i s based on the use o f a f i n e r p a r t i c l e ground scrap t i r e rubber crumb which i s blended or blown i n t o the asphalt a t the hot mix plant. The mesh s i z e o f t h i s crumb rubber ranges i n s i z e from .6mm to .18mm. Of the v a r i o u s processes, work to date has favored the "wet process" which i n 1993 represented the m a j o r i t y o f asphalt rubber tonnage. However, the relative production infancy of asphalt rubber technology suggests that an i n c r e a s i n g number o f formulations and m a t e r i a l s combinations u s i n g scrap t i r e rubber crumb w i l l be developed. As the knowledge of new highway construction materials and t h e i r p r o p e r t i e s and performance i s learned through a c t u a l usage, pavement designs and formulations w i l l emerge t o improve p r o d u c t i v i t y , performance and c o s t .


205

206


CRM TECHNOLOGIES


_z_

X

NET PROCESS TECHNOLOGIES

DRY PROCESS TECHNOLOGIES

CRM i s blended with asphalt cement before mixing the CRM modified binder with the aggregate.

Crumb rubber materials are blended with the aggregate before adding the asphalt cement to the blended mixture. Mix production practices are similar to those used f o r conventional HMA. CRM i s added directly to the mixture: * i n a drum plant at the RAP opening; * i n a batch plant at the pugmill.

McDonald (batch) * CRM mixed i n a blending tank and reacted i n holding tank before introduction to

Continuous Blending * CRM and asphalt cement can be mixed just before the binder i s introduced or i t can be mixed and stored i n a tank for l a t e r use

PlusRide

Generic Dry

* 15-22% (by weight •5-20% (by weight of of binder) of a binder) of a finer 10-30 mesh CRM. grind of CRM.

Source: National Center for Asphalt Technology

Figure 1. Comparison of wet and dry processes for incorporating ground rubber into asphalt.


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Rubber Recycling: Emerging Markets and New Technology207

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The progress to date i s dramatic proof of the t e c h n i c a l merits of t h i s new m a t e r i a l . Its i n i t i a l success has been based on i t s cost and t e c h n i c a l performance i n s e r v i c e . While the national debate continues on the mandated uses of asphalt rubber binder i n F e d e r a l l y funded highway c o n s t r u c t i o n p r o j e c t s , what f o l l o w i s the 1993 status p r i o r to the e f f e c t i v e date of the mandate. Current Status - A s p h a l t Rubber Asphalt rubber a p p l i c a t i o n s are proceeding and g a i n i n g acceptance on t h e i r technical merits. While the m a j o r i t y of usage through 1993 remained i n a group of western s t a t e s dominated by C a l i f o r n i a , Arizona and Texas, t h i s base of acceptance i s growing and now includes strong support i n s t a t e s such as F l o r i d a i n the Eastern United States. The p r e f e r r e d technology to date i s the wet process with the dominant usage being i n a top open graded mix r e s u r f a c i n g l a y e r of asphalt rubber. Costs are r a p i d l y d e c l i n i n g with the increased volume and c o n t r a c t o r experience from $400/ton down to $200/ton over the p e r i o d 1992-94. With the o r i g i n a l McDonald patents having expired i n 1992, more asphalt rubber a p p l i c a t i o n c o n t r a c t o r s are becoming i n v o l v e d and are expanding the c a p a c i t y base of t h i s new technology with increased b i d d i n g resulting. The Charles McDonald patent was based on h i s work i n the 1960 s as a m a t e r i a l s engineer f o r the C i t y of Phoenix, Arizona, to use a v u l c a n i z e d crumb rubber a d d i t i v e i n the asphalt cement mix i n order to develop a h i g h l y e l a s t i c m a t e r i a l f o r the r e p a i r of asphalt pavement. Ground crumb rubber in asphalt in 1993 is estimated to t o t a l more than 50 m i l l i o n pounds i n the USA (Figure 2), d r a m a t i c a l l y up from the l e s s than 20 m i l l i o n pounds i n 1991, with current f o r e c a s t usage i n 1994 of approximately 75 m i l l i o n pounds. This usage i s expected to grow to 250 m i l l i o n pounds annually by the end of the 90's. Thus by 1994, the e x i s t i n g 1990 b a s i c crumb rubber c a p a c i t y (estimated at 250 m i l l i o n pounds) would have been s o l d out had the i n d u s t r y ' s expansion not have been energized by scrap t i r e l e g i s l a t i o n events of the l a t e 80 s and e a r l y 90's. Ground rubber use i n "crack s e a l e r " f o r highway maintenance has now reached a 10 m i l l i o n pounds/year usage and i s growing s t e a d i l y i n acceptance, f u r t h e r proof of the v e r s a t i l i t y of asphalt rubber m a t e r i a l s i n t h i s a p p l i c a t i o n . f

f



Figure 2. Crumb rubber usage in the United States. Estimated CRM usages (in asphalt rubber applications).


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Rubber Recycling: Emerging Markets and New Technology 209

Automotive Uses


In a d d i t i o n to the "asphalt rubber" ground crumb requirements, we see a d d i t i o n a l f o r c e s now at work which should add f u r t h e r momentum to t h i s growing usage of ground rubber crumb i n i n d u s t r i a l applications. These f o r c e s are a combination of the growing corporate environmental awareness best d e f i n e d by the recent commitments by Ford, C h r y s l e r and General Motors to a recycling emphasis exemplified by the f o l l o w i n g excerpts: Ford Motor Company Guidelines (excerpt) P r o t e c t i n g the environment has always been important, but today, i t i s becoming i n c r e a s i n g l y more important. An area of s i g n i f i c a n t potential b e n e f i t to the environment i s i n c r e a s e d rubber r e c y c l i n g . We are focusing upon the use o f r e c y c l a t e i n our components and r e c y c l i n g o f components at the end o f v e h i c l e l i f e . Ford b e l i e v e s that most of our elastomer m a t e r i a l s u p p l i e r s are already i n v o l v e d i n r e c y c l i n g ( e s p e c i a l l y in-process scrap) and w i l l a l s o be r e c y c l i n g more materials i n the f u t u r e . Knowledge about these elastomer recycling efforts i s of value to Ford. Consequently, we would l i k e to know the f o l l o w i n g . A 1993 Ford i n q u i r y o f s u p p l i e r s i n c l u d e d the f o l l o w i n g questions. * Are you r e c y c l i n g rubber now? * What type of m a t e r i a l i s being r e c y c l e d ? * How much m a t e r i a l i s being r e c y c l e d ? * Is i t post-consumer or in-process scrap? * What i s i t s u l t i m a t e u t i l i z a t i o n ? * What are the s u p p l i e r ' s f u t u r e plans f o r i n c r e a s e d recycling? These questions were to be asked of the appropriate people w i t h i n the o r g a n i z a t i o n to a s s i s t Ford i n i t s evaluation. Ford Motor Company, with s u p p l i e r help, i s striving to be the nation's leader i n producing recyclable v e h i c l e s and i n the use o f r e c y c l e d m a t e r i a l s . The purpose o f t h i s l e t t e r i s to ensure that you are aware o f Ford's commitment to these o b j e c t i v e s , and to provide you with information about some o f our initiatives. To a i d us i n accomplishing our goal, Ford has p u b l i s h e d the "Ford Worldwide R e c y c l i n g G u i d e l i n e " . This g u i d e l i n e i s intended to provide recycling d i r e c t i o n to Ford Engineering a c t i v i t i e s and Program Managers and i s made up of three sections: FASTENERS/MATERIAL SELECTION/COMPONENT DESIGN.



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General Motors CorporationMaterial Selection G u i d e l i n e - GM-1000M (excerpt) MaterialUse recycled materials select materials f o r which recycling technologies are currently practiced. Use r e c y c l e d m a t e r i a l s - s e l e c t m a t e r i a l s that have been r e c y c l e d . M a t e r i a l S e l e c t i o n - Use r e c y c l e d m a t e r i a l s , s e l e c t rubber m a t e r i a l s f o r which r e c y c l i n g technologies are currently practiced. Consider r e c y c l i n g technologies that produce the greatest m a t e r i a l value. Investigate thermoplastic elastomers (TPE) as an a l t e r n a t i v e to thermoset rubber. TPE's are c u r r e n t l y e a s i e r to r e c y c l e than thermoset rubber. They can be reground and reused. R e c y c l i n g options f o r thermoset rubber. Regrind a percentage o f reground rubber can be put i n t o p a r t s that do not have s t r i n g e n t performance requirements. Devulcanization - two methods of d e v u l c a n i z i n g rubber (chemical and microwave). The r e s u l t i n g m a t e r i a l can be put i n t o v i r g i n m a t e r i a l i n l i m i t e d q u a n t i t i e s . This technology appears to be s t i l l i n the development stage. Use of recycled materials. Select rubber m a t e r i a l s that have r e c y c l e d content. Automotive grade thermoset rubbers used f o r weatherstrips, motor mounts, t i r e s , hoses, b e l t s , s e a l s and gaskets do not c u r r e n t l y c o n t a i n r e c y c l e d m a t e r i a l . Thermoset rubber p a r t s such as mats and truck bed l i n e r s can be made with a percentage o f reground rubber m a t e r i a l . Automotive grade TPE's could contain reprocessed p l a n t scrap. These excerpts make i t c l e a r that, these goals will energize the p a r t i c i p a n t s to seek s o l u t i o n s u t i l i z i n g e x i s t i n g technologies to recover as much as i s " c u r r e n t l y f e a s i b l e " using r e c y c l i n g c a p a c i t i e s and technologies, and i n a d d i t i o n , press f o r new and innovative s o l u t i o n s from new developing technologies. There are s e v e r a l emerging r e c y c l i n g technologies now i n development that w i l l add s i g n i f i c a n t l y to the achievement o f pre- and post-consumer rubber r e c y c l i n g goals now being s e t by the automotive i n d u s t r y . They i n c l u d e new surface treatment technologies a p p l i c a b l e to ground rubber p a r t i c l e s to s u b s t a n t i a l l y improve adhesion, wetting, processing and bonding. This on-going work includes polymeric surface coatings now being promulgated by both U.S. and European companies, along with a r e c e n t l y developed technology c a r r i e d out under Department o f Energy sponsorship which exposes r e c y c l e d rubber p a r t i c u l a t e to a r e a c t i v e c h l o r i n e gas mixture that chemically a l t e r s the surface o f the rubber p a r t i c l e s . At present, surface treatment particulate i s being



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evaluated f o r use i n a wide v a r i e t y o f automotive a p p l i c a t i o n s that, based on i n i t i a l t e s t r e s u l t s , w i l l most certainly benefit the automotive goals f o r increased r e c y c l e d rubber usage i n the coming decade. As can be seen from the "estimated r e c y c l a b l e m a t e r i a l s i n a 2400 pound v e h i c l e " (Figure 3) we have 140 pounds o f post-consumer rubber as a target, p l u s the manufacturing waste generated to produce these components. I f the o f t e n s t a t e d goal i s to achieve 25% rubber r e c y c l i n g content i n automotive components ( i . e . 35 pounds per automotive unit) t h i s would r e s u l t i n an annual requirement f o r r e c y c l e d rubber m a t e r i a l supply of approximately 375 m i l l i o n pounds. This w i l l create a s u b s t a n t i a l new market opportunity f o r r e c y c l e d rubber m a t e r i a l s and emerging technologies over the next decade. Footwear Uses T y p i c a l of s e v e r a l newly emerging ground rubber/molded rubber applications i n which work i s now being s u c c e s s f u l l y completed, i s i n the footwear i n d u s t r y . Here the emphasis i s on the development of both thermoplastic and thermoset compounds u t i l i z i n g f i n e l y ground rubber i n a wide assortment of shoe s o l e and c o n s t r u c t i o n components at s i g n i f i c a n t incorporation l e v e l s ranging from 20-50% of f i n e l y ground scrap t i r e rubber crumb. This emerging usage i s being heralded by the footwear i n d u s t r y as a means to capture USA based market share, i n response to a concerned buying p u b l i c for increased usage of r e c y c l e d m a t e r i a l s i n acceptable product a p p l i c a t i o n s . Such a program i s exemplified by a new shoe company founded f o r the purpose o f making a product e n t i r e l y from r e c y c l e d m a t e r i a l s . Figure 4 shows a shoe sole f a b r i c a t e d by the company with the use of up to 50% o f post-consumer scrap t i r e rubber to produce a s o l e that meets or exceeds a l l i n d u s t r y standards f o r wear, comfort and performance. We are c u r r e n t l y seeing such activities throughout the footwear industry, suggesting that a major market p o t e n t i a l i s developing for substantial usage of ground rubber i n both thermoset and thermoplastic molded shoe components. The United States' annual market f o r shoes t o t a l s approximately 1.2 b i l l i o n p a i r s . The average shoe s o l e weights between 0.75 and 1.0 pound per shoe s o l e . The "comfort shoe" p o r t i o n of t h i s t o t a l USA market i s the i n i t i a l area i n which ground rubber i s now being incorporated. This market t o t a l s between 375 to 425 m i l l i o n p a i r s . In a d d i t i o n , work i s a l s o p r o g r e s s i n g s u c c e s s f u l l y i n "work shoe" a p p l i c a t i o n s .


211


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Figure 3. Estimated recyclable material in a 2400 pound vehicle.

Figure 4. Shoe sole derived from post-consumer scrap tire rubber. (Courtesy of Deja Shoe Company.)



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With ground rubber i n c o r p o r a t i o n at only a 20% l e v e l , t h i s would represent an annual usage of between 120 and 150 m i l l i o n pounds per year. C u r r e n t l y we have reports of a number of shoe s o l e manufacturers at the 25% l e v e l and higher. The shoe s o l e i n Figure 4 has a 50% i n c o r p o r a t i o n l e v e l of r e c y c l e d rubber and meets or exceeds a l l abrasion, durometer, scuff-mark, other performance and q u a l i t y requirements to s a t i s f y the market place f o r a q u a l i t y comfort shoe s o l e at a competitive c o s t . Thus, the shoe sole market i s confirming that the use of recycled rubber p a r t i c u l a t e can provide excellent r e s u l t s while using a much higher i n c o r p o r a t i o n l e v e l without s a c r i f i c i n g q u a l i t y and performance. These r e s u l t s t r u l y exemplify the goals of a s u c c e s s f u l rubber r e c y c l i n g i n d u s t r y . Innovation - u t i l i z i n g new r e c y c l i n g technology. Quality maintaining customer demands f o r quality. Performance - at no s a c r i f i c e i n performance. Cost e f f e c t i v e s o l u t i o n s . Tires In f u r t h e r response to these automotive i n d u s t r y goals for r e c y c l i n g , we continue to b e l i e v e that the t i r e i n d u s t r y based on work from an e a r l i e r study and presented at the Rubber D i v i s i o n , ACS meeting h e l d i n Washington, DC (October 1990; Paper No. 15) (3); has an e x c e l l e n t p o t e n t i a l f o r cost savings and increased r e c y c l e d rubber usage without a s a c r i f i c e i n o v e r a l l t i r e performance (4). We have excerpted from the referenced study, s e v e r a l t a b l e s i n support o f our conclusions. This data i s summarized i n the f o l l o w i n g c h a r t s : T i r e Components-Ground Rubber Usage (Table II) Passenger T i r e Usage (Table III) Cost Savings per Unit (Table IV) P o t e n t i a l Cost Savings at 5% and 10% (Table IV) Raw M a t e r i a l Savings (Figure 6) Table II which sets f o r t h the s p e c i f i c tire c o n s t r u c t i o n elements of a passenger t i r e (Figure 5) i n which r e c y c l e d rubber can be u t i l i z e d , reflects a consensus of experienced tire manufacturing technologists and current tire performance manufacturing p r o c e s s i n g c a p a b i l i t i e s . The r e s u l t i n g minimum incorporation levels of r e c y c l e d rubber as a p p l i e d to the s e l e c t e d components results i n a projected usage level per average passenger t i r e o f between 2.3 t o 3.6% o f the t i r e weight (Portrayed i n Table III) . This t r a n s l a t e s i n t o


213


214


Table I I .

Passenger T i r e Components i n which a Fine P a r t i c l e Size Ground Rubber can be used Biaa

Radial—

INNERLINER

YES

YES

PLYCOAT

YES

YES

BEAD INSUL

NO

NO

CHAFER

YES

NO

APEX

YES

NO

COVERSTRIP

NO

NO

BLACK SIDEWALL

YES

NO

WHITE SIDEWALL

NO

NO

BELT

YES

NO

TREAD CAP

YES

YES

ONDERTREAD

YES

NO

Tablg I I I .

P a a a ^ r T i r e Osage of Finely Ground RnhbfT at, 5%

Cfflmpttrmnfr

%

% Gbmrmd

TREAD

29

5

ONDERTREAD

6

5

-

CARCASS

8.5

5

.43

.43

LINER

8.5

5

.43

.43

5

. 55

BLACK SIDEWALL

11

BEAD INSULATION

1

CHAFER/APEX

8

BELT

7

TIRE WEIGHT POUNDS GROUND RUBBER PER TIRE

ffnhb^r

Bias

£adial_

1.45

1.45

-

5

. 40

-

"

3.26%

2.31%

20

20

.65#


.462*



!-»

I

Ϊ

I

I

I

«3.

&

i

a

s

00

I-*


216

Tabic iv,

Cost Savings per u n i t using F i n e l y ground Ruhbrr at 5% & 10%


gCgCCat

^"T^Tgffr

JTiares

Track

Tlrea

5%

$0.0980

$0.5424

10%

$0.1861

$1,031

Based on o i l a t $20/barrel

AT 5%

AT 10%

185 M i l l i o n pounds

370 M i l l i o n pounds

Equals approximately: 15 m i l l i o n t i r e s r e c y c l e d

Equals approximately: 30 m i l l i o n t i r e s r e c y c l e d

Figure 6. Potential raw material 5% and 10%.

using finely ground rubber added at


18.

SMITH

Rubber Recycling: Emerging Markets and New Technology 217


an economic b e n e f i t based on t y p i c a l costs f o r the s u b s t i t u t e d r e c y c l e d rubber of approximately $.10 to $.18 per passenger t i r e and approximately $.50 to $1.00 per truck t i r e . This cost b e n e f i t to the producer could r e a d i l y support the cost o f developing the f i n a l compounds, processes and performance t e s t s r e q u i r e d to increase the usage of r e c y c l e d rubber m a t e r i a l back i n t o t i r e s and to increase the post-consumer rubber waste recovery being sought by the automotive i n d u s t r y . Such a program could add some 180 m i l l i o n pounds to the ground rubber annual usage f o r e c a s t (Figure 6). One very promising and l o g i c a l p l a c e to s t a r t would be i n the tread area of the mini-spare. Promising

New

Technologies

There are s e v e r a l promising new technologies emerging to provide improved r e c y c l e d rubber choices to the product designer, compounder and manufacturer o f rubber goods. These choices now include f i n e r p a r t i c l e s i z e s , s e v e r a l surface treatments and s e v e r a l thermoplastic elastomer materials which have successfully incorporated r e c y c l e d rubber at s u b s t a n t i a l l e v e l s using v u l c a n i z e d f i n e l y ground rubber p a r t i c u l a t e from t i r e s and pre-consumer waste rubber to d e l i v e r uniform p r o p e r t i e s and c o n s i s t e n t q u a l i t y f o r the manufacture of automotive and footwear components. Added to these now commercially available technological innovations are s e v e r a l more recent developments i n devulcanization of polymers with improved p r o p e r t i e s over those o f the long e s t a b l i s h e d "reclaimed" rubbers produced by vintage technologies d a t i n g to the 1940's. The d e v u l c a n i z a t i o n technologies employed i n c l u d e both dry and wet chemical processes and u l t r a s o n i c s . Each of these are c l a i m i n g improved c o s t s , acceptable environmental operating conditions and higher performance p r o p e r t i e s than those of the reclaimed m a t e r i a l s c u r r e n t l y produced. These p r e l i m i n a r y claims will be t e s t e d and confirmed by a growing d e s i r e to add such m a t e r i a l to the r e c e n t l y expanded f a m i l y of u s e f u l r e c y c l e d rubber materials a v a i l a b l e to meet a growing demand f o r r e c y c l e d rubber m a t e r i a l s that can provide q u a l i t y , performance and p o t e n t i a l cost b e n e f i t s to the markets now served by the rubber i n d u s t r y . Current and Future Market Outlook As d i s p l a y e d i n Table V, Figures 7 and 8, we foresee a dramatic increase i n the usage o f ground rubber



218


Table V.

F o ^ a t

of Ground ttiihher Crnmb Usage i n USA bv Year 2QQ3

Category

M i l l i o n * of Pormri* (See Figure 7)

ASPHALT RUBBER AMD HIGHWAY APPLICATIONS

420

38%

TIRES - PNEUMATIC/RETREAD MATERIALS AND OEM AND REPLACEMENT PASSENGER AND TRUCK

115

10%

155

14%

165

15%

CARPET, FLOORING, ROOFING, PADDING, ATHLETIC SURFACE AND CONSTRUCTION MATERIALS

155

14%

ALL OTHER APPLICATIONS INCLUDING PLASTIC, RUBBER MATERIALS

105

9%

SHOE SOLES-FABRIC AND COMPONENTS - ALL TYPES OF FOOTWEAR

AUTOMOTIVE/APPLIANCE AND OTHER MOLDED GOODS/AUTOMOTIVE, ETC.


SMITH



18.

Figure 8. Year 2003 projected ground rubber potential usage.


219

220



p a r t i c u l a t e from the current estimate o f 200 m i l l i o n pounds to over 1.1 b i l l i o n pounds, d r i v e n by a d i v e r s e set o f new technology driven applications i n automotive, highway c o n s t r u c t i o n , b u i l d i n g products, footwear, t i r e s and p l a s t i c rubber compounds. These p r o j e c t e d usages c l e a r l y d i s p l a y a need f o r a r a p i d l y expanding q u a l i t y r e c y c l e d rubber m a t e r i a l to meet the market p o t e n t i a l f o r cost e f f e c t i v e and performance d r i v e n s o l u t i o n s . This presents both an opportunity and a challenge o f s u b s t a n t i a l p r o p o r t i o n to t h i s growing i n d u s t r y . In summary, as we review the rubber r e c y c l i n g progress being made, most impressive i s the broad base of current a c t i v i t y at a l l l e v e l s o f the system to promulgate s o l u t i o n s to meet the rubber r e c y c l i n g challenge o f our i n d u s t r y and our n a t i o n . Literature Cited 1

Ball,

J . M.,

i n "Vanderbilt

Rubber

Handbook",

R. T.

V a n d e r b i l t Co., Norwich, Ct., 1978. Smith, F. G. and Klingensmith, W., Paper No. 15, Presented at the Fall Meeting of the Rubber D i v i s i o n , American Chemical Society, Washington, D.C., October 9, 1990. 2

3

"Fine

Particle

Rubber

Technology:

Butyl

Rubber",

Midwest Elastomers Inc., 1990. 4

Eckart,

D., Modern

Tire

Dealer,

June, 1980.

RECEIVED May 26, 1995


Rubber Recycling: Emerging Markets and New ... - ACS Publications

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