October 8, 2015

How To Improve Drafting Language In Chemical Arts Patents

Law360, New York (July 9, 2015, 10:28 AM ET) — Patentees in chemistry-based industries including the fuels, lubricants and chemical industries have special challenges in claiming their inventions. A patent is required to “conclude with one or more claims particularly pointing out and distinctly claiming the subject matter” to be protected. 35 U.S.C. § 112(b). Claims reciting physical properties, compositions and characteristics are common, but patentees sometimes use vague or ambiguous language, or do not properly define or disclosure how to measure a physical property.


In 2014, the U.S. Supreme Court revised the standard for definiteness under Section 112.Nautilus Inc. v. Biosig Instruments Inc., 134 S.Ct. 2120 (2014). The court held that “a patent’s claims, viewed in light of the specification and prosecution history, [must] inform those skilled in the art about the scope of the invention with reasonable certainty.”

The patent at issue in Nautilus claimed a heart rate monitor having electrodes in a “spaced relationship” with each other. On remand, the Federal Circuit determined that “spaced relationship” was definite under the “reasonable certainty” standard because the electrodes recited as having a “spaced relationship” are described in the specification as being located on a handle such that a person can grasp the handle and contact both electrodes with one hand. Therefore, a person of ordinary skill would understand that “spaced relationship” means the electrodes are far enough apart to be distinct and not further apart than the dimension of a hand. Noting that absolute precision is not required for definiteness due to the “inherent limitations of language,” the Federal Circuit affirmed its prior holding that the claims are not indefinite.

Vague Language

One way that claims in chemical areas can be indefinite is by using vague language. In the early case of United Carbon v. Binney & Smith, Co., 317 U.S. 228 (1942), the Supreme Court addressed the following claims:

1. Substantially pure carbon black in the form of commercially uniform, comparatively small, rounded, smooth aggregates having a spongy porous interior.

2. As an article of manufacture, a pellet of approximately one-sixteenth of an inch in diameter and formed of a porous mass of substantially pure carbon black.

The specification describes in some detail a process for making the inventive carbon black, and asserts that the process yields “substantially pure” carbon black in the form of pellets that

are very porous, of substantially spherical or globular form, have a somewhat lustrous outer surface which is not easily broken by handling, are more compact than untreated carbon, are fragile under light pressure, and may be easily reduced to soft minute particles which cannot be told from the original particles except that possibly they have a more unctuous feel.

The specification does not clarify terms such as “comparatively small,” “spongy,” “porous,” “smooth” and other vague terms in the claims. The court concluded that the claims are “inaccurate suggestions of the functions of the product” and do not “clearly circumscribe” what is sought to be protected.

The patent drafter in United Carbon might have chosen to define “comparatively small” using a numerical range or a measurable property, for example particle size of 10 µm to 500 µm. Instead of the vague term “comparatively small,” a precise but broad numerical range can provide broad coverage while satisfying the definiteness requirement. It is helpful, however, if the endpoints of the range have real significance. The drafter should understand, and may in some cases describe in the specification, what happens if the particle size is less than 10 µm or greater than 500 µm. By disclaiming any scope outside the range, potentially close prior art may be avoided, and any claims drawn to the range will have the advantage of precise end points.


Another way claims may be indefinite is if an unresolvable ambiguity results in an inability to determine the bounds of the claim. For example, claiming a polymer with a certain molecular weight may be an issue if a person of ordinary skill cannot determine how to measure it.

In Teva Pharms. USA Inc. v. Sandoz Inc., No. 13-854 (Jan. 20, 2015), the Supreme Court reviewed construction of the term “molecular weight” in a claim purporting to cover the drug Copaxone. According to Sandoz, a claim reciting “a molecular weight of 5 to 9 kilodaltons” was fatally indefinite because it was not clear which molecular weight was intended, the weight of the most prevalent molecule, the average weight of all the molecules, or an average in which heavier molecules count for more.

The district court considered testimonial evidence regarding the meaning of the term “molecular weight” and whether the specification sufficiently defined the term, and concluded that a skilled artisan would understand “molecular weight” to mean “peak average molecular weight.” The Federal Circuit disagreed, reviewing the case de novo and holding the claims indefinite. The Supreme Court held that the standard of review employed by the Federal Circuit was incorrect, and that findings of fact based on expert testimony are reviewed for clear error, while the ultimate legal conclusion is reviewed de novo. On remand, the Federal Circuit affirmed its prior holding (2015 U.S. App. LEXIS 10229, June 18, 2015).

The patentee might have avoided these issues by including in the patent a statement about which molecular weight was intended. Precisely, a mixture of different molecules does not have a molecular weight, because molecular weight is defined only in terms of the weight of a single molecule. Reciting “a molecular weight” of a mixture has no meaning. A mixture can have an average molecular weight, or the molecules of the mixture might fall into a molecular weight range. As noted in Teva, the average molecular weight may be defined as number-average, weight-average, z-average, or another type of molecular weight average. Including a definition in the specification or claims might have avoided the issue in Teva entirely.

New Properties

Sometimes, a patentee claims an unknown or undefined property of a material. In 2005, Dow Chemical Co. sued Nova Chemicals for patent infringement over imports of Nova’s SURPASS polyethylene plastic. See Dow Chem. Co. v. Nova Chems. Corp., 2012 U.S. App. LEXIS 7212 (Fed. Cir. 2012). The claims in Dow’s two patents recite “a slope of strain hardening coefficient greater than or equal to 1.3,” a Dow construct not previously known in the art.

The district court construed the phrase, although Nova alleged the Dow patents fail to set forth units for the coefficient and a figure purporting to illustrate the procedure for computing the coefficient is missing from the patent, and “numerous Dow engineers” including an inventor of one of the patents testified that they were unable to perform the calculation. According to Nova, the strain hardening coefficient is calculated from the slope of strain hardening and melt index of a material. The slope of strain hardening is determined by measuring the tensile properties of the material to generate a stress-strain curve, and drawing a line parallel to the “strain hardening region” of the stress-strain curve. The problem, according to Nova, is that depending on what area of the curve is designated the “strain hardening region,” slopes inside and outside the claimed range can be obtained.

On de novo review, the Federal Circuit affirmed the district court’s holding that the claims are not indefinite, and a petition for certiorari was denied (133 S.Ct. 544). The court noted expert testimony that stress-strain curves for plastics are “very, very well known” in the industry, so omission of the figure in the specification was not fatal. The court also noted that the patent described in text how to draw the line with some particularity, and includes examples that state units. “In sum, because one of skill in the art would understand the bounds of the claims,” the claims were not indefinite.


When claiming numerical properties or ranges, it may be important to specify how the property is measured. If there are many different ways to measure the property that may get meaningfully different results, it may be helpful to specify more than one way to measure.

In Honeywell Int’l Inc. v. U.S. International Trade Commission, 341 F.3d 1332 (Fed. Cir. 2003), the dispute centered on how to measure “melting point elevation” (MPE). The claims were drawn to methods of making polyethylene terephthalate (PET) yarn, and one step in the process results in a yarn with MPE within certain ranges. The specification defines MPE and describes an example test procedure. The specification does not, however, describe how to prepare the PET yarn specimen for DSC analysis. At the time, there were four different ways to prepare a sample, and the different methods yielded varying results. In this case, only one method, the “ball method,” was shown to produce MPE values for the accused yarns that fell within the claimed ranges.

The Federal Circuit determined that there were three possible constructions with respect to sample preparation based on the ball method, any one method, or all methods. The court could not adopt the ball method because the ball method appeared only in proprietary Honeywell documents. A method “outside the bounds of the claims, the written description, … the prosecution history, … [and] any written publication” would be an inappropriate basis for claim construction. The court could not choose a construction based on any one method because the various methods yielded greatly different results. The court could not adopt the all methods basis because Honeywell admitted that such a construction would render the invention inoperable. Not only is it important for claims to inform persons of ordinary skill of their scope with reasonable certainty, the claims must also “enable courts to determine whether novelty and invention are genuine.” See United Carbon, 317 U.S. at 236. Because the court could not find support for any conceivable construction of the term, the claims were indefinite.

The case of Wellman Inc. v. Eastman Chem. Co., 642 F.3d 1355 (Fed. Cir. 2011), is “very different” from Honeywell (Id at 1368). The Wellman patent has a claim that recites a polyethylene terephthalate resin having “a heating crystallization exotherm peak temperature of more than about 140 degrees Celsius. at a heating rate of 10 degrees Celsius. per minute as measured by differential scanning calorimetry.” The district court granted summary judgment of indefiniteness because the patent does not disclose sample conditions and test parameters for obtaining consistent differential scanning calorimetry (DSC) measurements.

The Federal Circuit disagreed, holding that a person of ordinary skill in the art would know how to perform the DSC test. The record reflected an international standard for performing such tests setting forth sample preparation procedures and testing protocols that would lead a person of ordinary skill to be able to perform the test consistently. The court held that the patent need not specifically recite or incorporate the standard since it was publicly available. Whereas, in Honeywell, the only information that would have aided a person of ordinary skill in the art in understanding the meaning of the claim was not publicly available, in Wellman an industry standard was available to aid in understanding, with reasonable certainty, the meaning of the claim.

In the chemical-based industries, patent claims often recite materials, physical properties, characteristics and effects. To avoid indefiniteness, drafters should pay attention to describing the invention in a way that persons of ordinary skill can understand what the various claim terms mean. Use of broad but precise terms with clear definitions is helpful in obtaining good coverage without risking indefiniteness. Vagueness should be avoided. Numerical ranges may be used to claim measurable properties and characteristics, but the end points of the ranges should have some significance. Describing measurement of the characteristic is also important. Persons of ordinary skill in the art should be able to tell, from reading the specification, how the characteristic is measured. Careful attention to communicating the invention clearly to a broad audience of ordinary artisans will achieve good results for inventors and assignees in the chemical-based industries.

—By Ronald G. Embry Jr., Patterson & Sheridan LLP

Ronald Embry is a partner in the Houston office of Patterson & Sheridan.

The opinions expressed are those of the author(s) and do not necessarily reflect the views of the firm, its clients, or Portfolio Media Inc., or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.

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