Wednesday, March 13, 2013

PBR – Rubber, Not Beer


It was always curious  the fear that college organic chemistry engendered in students. Yes, it could wrap your brain around the axle learning the various bond types, transition states, and compound-naming conventions, but come on, gang, it’s fascinating!

A recent posts featured a photo of a stack of tires. The Rubber Manufacturers Association estimates that 292 million tires weighing a total of 4.9 million tons, were scrapped in the US in 2009. The largest percentage of these (40.3%) were disposed of as tire-derived fuel, with the next largest category being ground rubber. For this end-use, molded and extruded products, sports surfacing, playgrounds/mulch/animal bedding, and automotive uses were the descending order of uses. The RMA also estimates that 162 million new tires were manufactured in the US in 2012.

A common thread between tires and your car, the roads you drive on, the tennis courts you play on, surgeries or medical implants and devices you might be treated with, and that evil-of-evils (not!), hydraulic fracturing (aka fracking), is polybutadiene rubber (PBR). Polybutadiene is a polymer (a chemical compound or mixture of compounds consisting of repeating structural units – proteins, DNA, and the polystyrene found in styrofoam are polymers.) first polymerized by Russian chemist Sergei Vasilyevich Lebedev in 1910. The compound is highly wear resistant, and about 70 percent of its production is used in tire manufacture.

Electrically conducting tires

One of the most recently issued patents related to the use of PBR in tires is US 8,376,005, “Pneumatic tire.” It was granted in February 2013 to Norihiko Nakamura (Osaka, Japan) and assigned to Toyo Tire & Rubber Co., Ltd., also of Osaka. His abstract summarizes the invention:

“A pneumatic tire that can be manufactured according to the conventional method without requiring special tire manufacturing steps and without needing addition of material members and production steps, has excellent rolling resistance and wet properties, and has conductivity. A pneumatic tire has a side wall contacted with a rim strip of a bead part and extended outward in a radial direction of a tire from the bead part to be coupled to a ground contact edge region of a tread part, the side wall comprising a two-layer structure of an internal layer rubber and an outer layer rubber, characterized in that on the circumference of unilateral or bilateral part of the tire, the rim strip and either the internal layer rubber or the external layer rubber of the side wall are formed into a continuous conductive path by a conductive rubber material, only the conductive path is used as a conducting path of the tire, and members other than the conductive path are selected and used from a conductive rubber material or a nonconductive rubber material.” Drawing references deleted for clarity.

As is common in modern tires, silica is used in the tread rubber. This leads to a problem, however: “With this silica compounding technology, static electricity charged in vehicles gives rise to the problems that discharge phenomenon is generated when a tire passes on manholes and the like, resulting in radio noise, adverse influence to electronic circuit parts, generation of short-circuit, and the like.”

Nakamura solves this static electricity problem by including a conductive rubber material in the tire tread. That conductive layer contains polybutadiene rubber.

Tires in your roads

“Asphalt rubber is the largest single market for ground rubber, consuming an estimated 220 million pounds, or approximately 12 million tires,” according to the USEPA. Ground tire rubber (including the PBR found in tires) can be blended with asphalt to provide longer-lasting road surfaces, reduced maintenance, lower road noise, and shorter braking distances.

Lance Allan and Jim Farnell (both of Santa Fe Springs, CA) have received one of the most recent patents related to rubber-containing asphalt – US 8,377,190, “Methods and arrangement for creating asphalt emulsion,” issued in February 2013. They provide “[a] method for creating asphalt emulsion …. The method includes heating a base asphalt. The method also includes injecting the base asphalt into a colloid mill. The method further includes breaking up the base asphalt into small particles. The method yet also include preparing a soap solution, wherein the soap solution includes an acid, water, and a first emulsifier, wherein the first emulsifier is an alkyl amines salt based emulsifier. The method yet further includes combining the small particles of the base asphalt with the soap solution to create the asphalt emulsion.” Their claim 6 specifies that the “base asphalt is a tire-rubber-modified asphalt”.

We considered pothole repair last year.

Athletic courts, concert stages

David Barlow (Seminole, FL) received US 8,266,857 in September 2012 for his invention “Interlocking floor system with barbs for retaining covering.” He provides “[a] flooring system includ[ing] multiple polymeric panels that are interlocked into a floor system and then covered with a material such as carpet and artificial turf. A top surface of the polymeric panels includes barbs to hold the material from moving laterally during use.” He envisions that his floor covering can be used on basketball courts, concert stages, as the finished surface for athletic courts, or as an underlayment for tennis courts or lawn bowling areas. The rubber in the panels “can include structural foam and processed recycled automobile tires mixed in a bonding agent.”

PBR in medicine

The synthetic rubber polybutadiene plays a role in the medical device industry. A recent invention in this art is US 8,303,973, “Multifunctional compounds for forming crosslinked biomaterials and methods of preparation and use,” granted in November 2012 (on Election Day, to be precise) to George Y. Daniloff and co-inventors and assigned to Angiotech Pharmaceuticals (US), Inc. (Seattle, WA). Daniloff et al.’s abstract states:

“Multifunctional compounds are provided that readily crosslink in situ to provide crosslinked biomaterials. The multifunctional compounds contain a single component having at least three reactive functional groups thereon, with the functional groups selected so as to be non-reactive in an initial environment and inter-reactive in a modified environment. Reaction of a plurality of the multifunctional compounds results in a three-dimensional crosslinked matrix. In one embodiment, a first functional group is nucleophilic, a second functional group is electrophilic, and at least one additional functional group is nucleophilic or electrophilic. Methods for preparing and using the multifunctional compounds, and kits including the multifunctional compounds are also provided. Exemplary uses for the multifunctional compounds include tissue augmentation, biologically active agent delivery, bioadhesion, and prevention of adhesions following surgery or injury.”

Polybutadiene is one of the ‘multifunctional compounds’.

Rubber in fracking fluids

We’ve considered in past posts the process of hydraulic fracturing and inventions related to various aspects of this process that is re-defining natural gas production, especially in the US. You can find them by searching here. A review of hydraulic fracturing fluid is here.

A team of Schlumberger Technology Corporation inventors led by Evgeny Barmatov were granted US 8,141,637, “Manipulation of flow underground”, in March 2012. Their invention relates to placement of propane in a formation, or to blocking unwanted flow paths in the underground rock. Their abstract states:

“Solid material required at a subterranean location is supplied from the surface suspended in a carrier liquid and agglomerated below ground by means of a binding liquid. To achieve agglomeration, the binding liquid and the particulate solid are similar to each other but opposite to the carrier liquid in hydrophilic/hydrophobic character. The solid and the binding liquid may both be hydrophobic while the carrier liquid is hydrophilic, or vice versa. The solid may be hydrophobically surface modified to render it hydrophobic. The binding liquid may be provided as a precursor which converts to the binding liquid below ground to trigger agglomeration after arrival at the subterranean location. The agglomerates may function as proppant heterogeneously placed in a fracture of a reservoir, or may serve to block an unwanted path of flow. The binding liquid may polymerise after agglomeration so as to stabilise and strengthen the agglomerates.”

According to claim 17, “the binding liquid undergoes polymerisation after the agglomeration has taken place.” The patent’s Specification clarifies that the binding liquid can contain polybutadiene - that same compound found in your tires.

PBR in fracking well cement

When oil and gas wells (including those used for hydraulic fracturing) are drilled, a long length of pipe (the casing) is placed in the wellbore and a cement slurry is then placed between the casing and the surrounding rock formation. Many factors determine the composition of the cement slurry (this is not like mixing a sack of concrete to fix your sidewalk or patio), including slurry density, rheology, pump time, fluid loss, settling and gas migration mitigation during placement and compressive strengths for long term performance, according to inventors B. Raghava Reddy and Krishna M. Ravi. They were granted US 7,913,757, “Methods of formulating a cement composition,” in March 2011. Their patent is assigned to Halliburton Energy Services. Inc.

Reddy and Ravi provide “[a] method of cementing a wellbore in a subterranean formation, comprising formulating a cement composition that may be suitable for long-term zonal isolation of the subterranean formation by evaluating a subterranean formation, preparing a base cement composition, determining the compressive strength of the base cement composition, determining the tensile strength of the base cement composition, and adjusting the ratio of compressive strength to tensile strength as need to within a first optimizing range to form a first optimized cement composition, and placing the optimized cement composition in the wellbore.” To adjust the strength of the slurry mixture they incorporate “an elastomer, a rubber” or a combination. One of the rubber compounds they specifically claim (claim 13) is cis–1,4-polybutadiene rubber - the same PBR used in tires.

Technologies cross

These inventions are examples of the cross-cutting nature of technology and how a given material, compound, process, or mechanism can be used across a very wide range of art. In addition, the nature of innovation is such that it is unpredictable, although much effort is spent on the part of industry to try to determine future innovation trends, in part from looking for “holes” in existing patterns of inventions (this is known as whitespace or gap analysis). A compendium of recent advances in clean technology can be found in Way Better Patents’ Green Tech Discovery and Analysis report.

A Bonus

You, your kids, or parents (or grandparents for that matter. Now that is stunning.) may have enjoyed using this PBR-based product. A hint – it hit the market in the mid–60s, and it has a resilience factor greater than 90%, which is a huge part of its appeal.