UNITED STATES DISTRICT COURT
`DISTRICT OF MINNESOTA
`
`3M Innovative Properties Co. and
`3M Company,
`
`Plaintiffs,
`
`v.
`
`GDC, Inc., and Monadnock
`Non-Wovens, LLC,
`
`Defendants.
`
`Civil No. 13-1287 (DWF/JJK)
`
`MEMORANDUM
`OPINION AND ORDER
`
`________________________________________________________________________
`
`Ariel O. Howe, Esq., David J. F. Gross, Esq., David R. Merritt, Esq., Elizabeth Cowan
`Wright, Esq., James W. Poradek, Esq., and Timothy M. Sullivan, Esq., Faegre Baker
`Daniels LLP, counsel for Plaintiffs.
`
`James K. Cleland, Esq., and Joshua E. Ney, Esq., Brinks Gilson & Lione; and Kurt J.
`Niederluecke, Esq., and Timothy M. O’Shea, Esq., Fredrikson & Byron, PA, counsel for
`Defendants.
`________________________________________________________________________
`
`INTRODUCTION
`
`This matter is before the Court on the issue of patent claim construction pursuant
`
`to Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996).
`
`BACKGROUND
`
`This litigation involves allegations by Plaintiffs 3M Innovative Properties Co. and
`
`3M Company (together, “3M”) that Defendants GDC, Inc. (“GDC”) and Monadnock
`
`Non-Wovens, LLC (“MNW”) (together, “Defendants”) are infringing one or more claims
`
`of U.S. Patent No. 5,773,375, entitled “Thermally Stable Acoustical Insulation” (the
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`“’375 Patent”), through the manufacture and sale of thermally stabilized insulation
`
`products. (Doc. No. 1, Compl., ¶¶ 11-15.)
`
`The ’375 Patent relates to a “thermally stable acoustical insulation microfiber web
`
`for attenuation of sound waves.” (Id. ¶ 7, Ex. A (“’375 Patent”) at c. 11, ll:38-39.) The
`
`invention of the ’375 Patent is embodied in 3M’s Thinsulate™ Acoustic Insulation
`
`(“TAI”) product. (Doc. No. 79, Wright Decl. ¶ 2, Ex. 5.) TAI is a nonwoven melt-blown
`
`material made of extremely small polypropylene and polyester microfibers. (See ’375
`
`Patent at c.1, ll:9-24.) In the early to mid-1990s, 3M was expanding the use of its
`
`Thinsulate™ technology to automotive and other industrial applications. (Wright Decl.
`
`¶ 2, Ex. 6 at 3M00001118.) TAI is used in automobiles for noise reduction. (Id. ¶ 2,
`
`Ex. 8.)
`
`3M’s first version of TAI was covered by U.S. Patent No. 5,298,694, entitled
`
`“Acoustical Insulating Web” (the “Thompson Patent”), which claims a method for
`
`attenuating sound waves, comprising steps including providing a non-woven acoustic
`
`insulation web with fiber diameter of less than about 15 microns, thickness of at least
`
`about 0.5 cm, density of less than about 50 kg/m3, and pressure drop of at least about
`
`1 mm water at a flow rate of about 32 liters/min. (Wright Decl. ¶ 2, Ex. 7 (the
`
`“Thompson Patent”) at c. 19, ll:38-47.) 3M’s first version of TAI provided several
`
`advantages over existing insulation, namely higher sound absorption per weight and
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`2
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`easier compressibility. (Wright Decl. ¶ 2, Ex. 9 at 3M00095951-52; id. ¶ 2, Ex. 8.)1 TAI
`
`includes two types of microfibers: polypropylene and polyester. (Id. ¶ 2, Ex. 11
`
`at 3M00170717-18.) The polypropylene fibers dissipate sound energy into heat. (Id.)
`
`The polyester fibers provide durability and loft retention. (Id.)
`
`3M manufactures its polypropylene melt-blown web as follows: polypropylene
`
`pellets are introduced into a hopper; the pellets are fed from the hopper to an extruder,
`
`where the pellets are subjected to pressure and heat so as to make them molten; the
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`molten pellets are pumped toward a blown-microfiber die; and, the polypropylene melt is
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`conveyed through the die that emits the polypropylene as extremely small microfibers
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`that are stretched and made thinner by hot air and then collected to make a microfiber
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`web. (Doc. No. 125, Osswald Decl. ¶ 23.)
`
`In 3M’s first version of the TAI, the polypropylene microfibers were susceptible
`
`to degradation at high temperatures and therefore could only be used in lower
`
`temperature areas of a car. (’375 Patent at c. 1, ll:11-27.) TAI was not recommended for
`
`use in areas that could become very hot, such as near the engine or surrounding the
`
`passenger cabin. 3M endeavored to solve the problem of degradation at high
`
`temperatures (or lack of thermal stability), the result being 3M’s thermally stable
`
`acoustical insulation claimed in the ’375 Patent.2 The ’375 Patent recites a thermally
`
`
`1
`Existing automotive acoustical insulation products included “shoddy,” which
`consists primarily of clumps of cotton fibers. (Wright Decl. ¶ 2, Ex. 9 at 3M00095951.)
`
`The inventors on 3M’s ’375 Patent are Michael D. Swan and Ruth A. Ebbens.
`
`(’375 Patent at [76].)
`
` 2
`
`
`
`3
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`stable acoustical insulation having a thermal stabilizer or antioxidant uniformly
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`distributed throughout the microfibers such that they are stable at 135°C for at least
`
`10 days. (’375 Patent at 7:30-39; 7:43-8:29;11:37-12:54.) The thermal stability of the
`
`insulation allows it to be used in more locations in cars than the original TAI, namely in
`
`areas that become hot. (Wright Decl. ¶ 2, Ex. 14.)
`
`
`
`In 2003, Defendants began selling Sonozorb®, a polypropylene melt-blown
`
`microfiber acoustical insulation that 3M alleges infringes the ’375 Patent. (Wright Decl.
`
`¶ 2, Ex. 20 at 1; id. ¶ 2, Exs. 21 & 22; Doc. No. 25, Answer, ¶¶ 47-52.)3 Today,
`
`Defendants advertise Sonozorb as acoustical insulation that will withstand temperatures
`
`of up to 110°C. (Wright Decl. ¶ 2, Ex. 22; Doc. No. 25 ¶ 52.)
`
`
`
`In a Complaint filed on May 29, 2013, 3M alleges that Defendants’ manufacture
`
`and sale of thermally stabilized acoustical insulation products under the brand name
`
`“Sonozorb” infringe the ’375 Patent. (Compl. ¶¶ 10-15.) Defendants deny 3M’s
`
`allegations and seek a declaration that the ’375 Patent is invalid and/or not infringed.
`
`DISCUSSION
`
`I.
`
`Claim Construction Principles and the Law of Indefiniteness
`
`A.
`
`Claim Construction
`
`Patent claim construction, i.e., the interpretation of the patent claims that define
`
`the scope of the patent, is a matter of law for the court. Markman v. Westview
`
`
`3
`More specifically, MNW manufactures the melt-blown polypropylene microfiber
`web and sells it to GDC, which then cuts the microfiber web into parts such as door
`panels. (Answer ¶¶ 47-52; Wright Decl. ¶ 2, Ex. 21.)
`
`
`
`4
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`Instruments, Inc., 52 F.3d 967, 970-71 (Fed. Cir. 1995), aff’d, 517 U.S. 370 (1996).
`
`Proper claim construction requires an examination of the intrinsic evidence of record,
`
`including the claim language, the specification, and the prosecution history. Bell Atl.
`
`Network Servs., Inc. v. Covad Commc’ns Grp., Inc., 262 F.3d 1258, 1267 (Fed.
`
`Cir. 2001); Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed. Cir. 1996).
`
`The starting point for claim construction is a review of the words of the claims
`
`themselves. Phillips v. AWH Corp., 415 F.3d 1303, 1312 (Fed. Cir. 2005) (en banc)
`
`(citation omitted); see also Vitronics, 90 F.3d at 1582 (“First, we look to the words of the
`
`claims themselves, both asserted and unasserted, to define the scope of the patented
`
`invention.”). The words of a claim generally carry “the meaning that the term would
`
`have to a person of ordinary skill in the art at the time of the invention.” Phillips, 415
`
`F.3d at 1313; see also Bell Atl., 262 F.3d at 1367 (“As a starting point, we give claim
`
`terms their ordinary and accustomed meaning as understood by one of ordinary skill in
`
`the art.”).4
`
`Claims must also be read in view of the specification. Phillips, 415 F.3d at 1315.
`
`The specification is always “highly relevant” to claim construction and “the single best
`
`guide to the meaning of a disputed term.” Id. (citing Vitronics, 90 F.3d at 1582.) The
`
`specification “necessarily informs the proper construction of the claims.” Phillips, 415
`
`F.3d at 1316 (explaining that the claims must be construed so as to be consistent with the
`
`specification) (citation omitted).
`
`4
`The Court refers to a “person of ordinary skill in the art” and “skilled artisan”
`interchangeably throughout this Order.
`
`
`
`5
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`Generally, there is a heavy presumption in favor of the ordinary meaning of claim
`
`language, as understood by one skilled in the art. Bell Atl., 262 F.3d at 1268. However,
`
`the specification may prescribe a special definition given to a claim term that differs from
`
`the meaning it would otherwise possess, or it may reveal a disavowal or disclaimer of
`
`claim scope by the inventor. Phillips, 415 F.3d at 1316. In such cases, the intention that
`
`is expressed by the inventor in the specification is dispositive. Id. The Court may not,
`
`however, import limitations from the specification into the claims. Id. at 1323. To avoid
`
`importing limitations from the specification into the claims, the Court considers that the
`
`purposes of the specification are to teach and enable those of skill in the art to make and
`
`use the invention and to provide a best mode for doing so. Id.
`
`The Court should also consider the patent’s prosecution history, which provides
`
`evidence of how the United States Patent and Trademark Office (“USPTO”) and the
`
`inventor understood the patent. Id. The prosecution history “consists of the complete
`
`record of the proceedings before the [USPTO] and includes the prior art cited during the
`
`examination of the patent.” Id. The prosecution history may “inform the meaning of the
`
`claim language by demonstrating how the inventor understood the invention and whether
`
`the inventor limited the invention in the course of prosecution, making the claim scope
`
`narrower than it would otherwise be.” Id. (citing Vitronics, 90 F.3d at 1582-83). The
`
`doctrine of prosecution disclaimer “preclude[s] patentees from recapturing through claim
`
`interpretation specific meanings disclaimed during prosecution.” Omega Eng’g Inc. v.
`
`Raytek Corp., 334 F.3d 1314, 1323 (Fed. Cir. 2003).
`
`
`
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`A court may, in its discretion, consider extrinsic evidence, though such evidence is
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`less reliable than intrinsic evidence. Phillips, 415 F.3d at 1317-18. In most situations,
`
`intrinsic evidence will resolve any ambiguity in a disputed term, and when it does so, the
`
`court may not rely on extrinsic evidence. Vitronics, 90 F.3d at 1583.5
`
`B.
`
`Indefiniteness
`
`Defendants argue that several claim terms of the ’375 Patent are invalid because
`
`they are indefinite. Because a patent is presumed valid, “[t]he party challenging the
`
`patent bears the burden of proving invalidity by clear and convincing evidence.” Takeda
`
`Pharms. Co. v. Zydus Pharms. USA, Inc., 743 F.3d 1359, 1366 (Fed. Cir. 2014). The
`
`United States Supreme Court recently articulated the relevant standard applicable to the
`
`definiteness requirement. See Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120,
`
`2128-30 (2014). Under this standard, a patent’s claims, when “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.” Id. (emphasis added). In Nautilus, the
`
`Supreme Court recognized that “absolute precision” was not attainable and that some
`
`“modicum of uncertainty . . . is the price to be paid for appropriate incentives for
`
`innovation.” Id. The Supreme Court nonetheless confirmed that a patent “must be
`
`precise enough to afford clear notice of what is claimed, thereby apprising the public of
`
`what is still open to them.” Id. (internal quotation marks omitted).
`
`
`5
`Here, as discussed below, the meaning of the disputed claim limitations can be
`determined with intrinsic evidence, and there is no need to rely on extrinsic evidence.
`
`
`
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`Patents are not directed to lawyers or the public generally, but they are directed to
`
`those skilled in the relevant art. Id. Indefiniteness is, therefore, gauged from the
`
`perspective of one of skill in the art as of the time of the patent application. See id. at
`
`2130. A patent need not include “information readily understood by practitioners lest
`
`every patent be required to be written as a comprehensive tutorial and treatise for the
`
`generalist, instead of a concise statement for persons in the field.” Verve, LLC v. Crane
`
`Cams, Inc., 311 F.3d 116, 119-20 (Fed. Cir. 2002).
`
`II.
`
`Test Evidence and Motion to Exclude
`
`A.
`
`Test Evidence
`
`Many of Defendants’ arguments on indefiniteness relate to the testing of certain
`
`limitations in the ’375 Patent. Because the issues regarding testing permeate many of the
`
`claims, the Court addresses the testing issue first. With respect to several claims, for
`
`example, Defendants assert that certain limitations are indefinite because the ’375 Patent
`
`does not identify a particular test that should be used to establish the existence of a
`
`limitation, or that there are multiple available tests and their use would yield different
`
`results. In general, Defendants assert that the lack of specificity regarding appropriate
`
`testing methods render certain claims indefinite.
`
`Although the Court will address certain arguments in more detail below, the Court
`
`notes from the outset that the disagreements with regard to testing are more appropriately
`
`addressed in the context of an infringement analysis. See, e.g., ADC Telecomm., Inc. v.
`
`Switchcraft, Inc., 281 F. App’x 989, 992 (Fed. Cir. 2008) (“The parties’ dispute over the
`
`proper testing method is [] a factual question that the district court properly submitted to
`
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`the jury.”); Union Carbide Chem. & Plastics Tech. Corp. v. Shell Oil Co., 425 F.3d 1366,
`
`1377 (Fed. Cir. 2005) (“Because the claim language does not require a particular form of
`
`testing, this inquiry is not a claim construction question.”), overruled on other grounds by
`
`Cardiac Pacemakers, Inc. v. St. Jude Med., Inc., 576 F.3d 1348 (Fed. Cir. 2009); Takeda,
`
`743 F.3d at 1366-67 (“[T]he mere possibility of different results from different
`
`measurement techniques” does not render a claim indefinite.). The disputes over testing
`
`methods do not support a finding of indefiniteness. Instead, the Court anticipates that the
`
`numerous disputes with respect to proper testing methods will be raised in the context of
`
`infringement and perhaps in a Daubert motion.
`
`B. Motion to Exclude
`
`The Court will briefly address 3M’s pending Motion to Exclude Defendants’
`
`Untimely Expert Report on Indefiniteness Issues (Doc. No. 96), which was filed shortly
`
`before the Markman hearing. In its motion to exclude, 3M objects to Defendants’ use of
`
`the expert report of David Cook, Ph.D. (“Exova Testing Report”)6 in any manner to
`
`support its indefiniteness contentions because it was untimely.
`
`Defendants submit that the test results in the Exova Testing Report were both
`
`properly and timely submitted. Defendants assert that 3M originally proposed that the
`
`time and temperature term (discussed below) be given its plain and ordinary meaning, but
`
`6
`Defendants deny that the report to which 3M objects is an “expert report,” and
`instead submit that 3M is objecting to test results (the “Exova Testing”) that were
`commissioned by Defendants’ expert Dr. Stephen Spiegelberg. For ease of reference, the
`Court refers to the report as the “Exova Testing Report.”
`
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`later submitted an alternative proposed claim construction, including one in which the
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`time and temperature term encompasses two different test protocols—a “dome” test and a
`
`“tray” test.7 Defendants submit that they commissioned Exova, a Canadian firm, to
`
`conduct an experiment to determine whether samples subjected to the “dome” and “tray”
`
`tests perform similarly and to respond to Dr. Osswald’s opinion regarding the test
`
`protocols. Based on the results of the Exova tests, Dr. Spiegelberg opined that the tests
`
`would yield different results. (Doc. No. 123, Spiegelberg Rebuttal Decl. ¶¶ 84-87.)
`
`Defendants also argue that the Exova Testing Report is not an expert report, but rather it
`
`is simply a test commissioned by Dr. Spiegelberg to attach to his rebuttal declaration.
`
`Defendants assert that because the scheduling order permits rebuttal declarations, the
`
`Exova Testing Report was proper and timely.
`
`On November 21, 2014, Defendants submitted the rebuttal declaration of
`
`Dr. Spiegelberg, to which the Exova Testing Report was attached. The Exova Testing
`
`Report contains the results of a series of heat aging experiments conducted by Exova on
`
`behalf of Defendants’ counsel. (Doc. No. 99, Sullivan Decl. ¶ 3, Ex. A (“Exova Testing
`
`Report”); id. ¶ 3, Ex. E.) The experiments were conducted on samples of melt-blown
`
`polypropylene microfiber acoustical insulation. (Exova Testing Report at 2.) At the end
`
`7
`In his declaration, 3M’s expert offered his opinion that a person of ordinary skill
`in the art would understand that the thermal stability test (for the claim language “for at
`least 10 days at 135° C”) did not specify the use of a forced air or convection oven or a
`particular air flow. (Osswald Decl. ¶ 126.) Further, 3M’s expert explained that there
`were two ways to minimize air flow around a sample when testing thermal stability:
`(1) place a sample in a tray having sides that act to prevent the direct impingement of air
`(the “tray” test); and (2) place a sample in a tray having sides that act to prevent the direct
`impingement of air and place another tray on top (the “dome” test). (Id. ¶¶ 127-28.)
`
`
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`of the experiments, Dr. Cook made several observations, including observations related
`
`to the color, dimensions, weight, and suppleness of the tested samples via visual
`
`examination. (Id.) 3M submits that these observations amount to an expert report and
`
`were untimely under the scheduling order and Rule 26(a)(2) of the Federal Rules of Civil
`
`Procedure and should be excluded under Rules 16(f) and 37(c)(1).
`
`According to this schedule, all initial expert declarations as to claim construction
`
`were due by October 21, 2014. Rebuttal declarations were permitted to be filed by
`
`November 21, 2014. Specifically, the scheduling order in this matter set forth the
`
`following deadlines pertaining to claim construction/indefiniteness: (1) Defendants were
`
`to serve initial expert declarations as to indefiniteness by September 23, 2014; (2) 3M
`
`was to serve its rebuttal expert declaration as to definiteness, and the parties were to
`
`simultaneously file Markman/indefiniteness opening briefs, as well as any initial expert
`
`declaration(s) as to claim construction by October 21, 2014; and (3) the parties were to
`
`simultaneously file Markman/indefiniteness rebuttal briefs, as well as any rebuttal expert
`
`declaration(s) as to claim construction by November 21, 2014. (Doc. No. 71 at 1-2.)
`
`Here, Defendants submitted two expert reports to support their indefiniteness
`
`arguments—Dr. Spiegelberg’s and Dr. Deborah Lickfield’s declarations. Despite not
`
`submitting any initial report by Dr. Cook, Defendants submitted the Exova Testing
`
`Report (which is signed by Dr. Cook and dated November 14, 2014) to 3M for use at the
`
`deposition of 3M’s expert Dr. Osswald and later submitted the Exova Testing Report as
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`an attachment to Dr. Spiegelberg’s rebuttal declaration.
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`
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`As a threshold matter, the Court notes that Defendants’ argument that the newly
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`commissioned test report is not an expert report is unpersuasive. In addition, Defendants’
`
`failure to disclose Dr. Cook as an expert on September 23, 2014, the date on which initial
`
`expert declarations on indefiniteness were due, appears to likely be a violation of that
`
`scheduling order. However, the Court need not decide whether the report should be
`
`excluded because, as the Court explained above, the Court has concluded that the
`
`question of indefiniteness will not be decided on the basis of disputed testing methods.
`
`Instead, most of the disputes over testing methods will be revisited at the infringement
`
`stage. Therefore, the Court denies the motion to exclude the Exova Testing Report as
`
`moot.
`
`III. The ’375 Patent
`
`A.
`
`Relevant Claim Language and Prosecution History
`
`The ’375 Patent is a product patent with seventeen claims, all directed at a
`
`“thermally stable acoustical insulation microfiber web” comprising certain elements.
`
`Specifically, independent Claim 1 of the ’375 Patent states:
`
`1. A thermally stable acoustical insulation microfiber web for
`attenuation of sound waves comprising a melt-blown polypropylene
`microfiber web having an average effective fiber diameter of less than
`about 15 microns, a thickness of at least about 0.5 cm, a density of less than
`50 kg/m3 and a pressure drop of at least about 1 mm water at a flow rate of
`about 32 liters/min., said polypropylene microfibers formed of
`polypropylene homopolymers, copolymers or blends thereof with a
`nonvolatile thermal stabilizer or antioxidant is uniformly distributed
`throughout the microfibers such that the microfibers are thermally stable for
`at least 10 days at 135° C.
`
`
`(’375 Patent at c. 11, ll:38-48.)
`
`
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`3M applied for the ’375 Patent on May 29, 1996. When originally filed, the
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`application included claims directed to a thermally stable acoustical insulation product, as
`
`well as claims directed to a method of forming a thermally stable acoustical insulation.
`
`(Wright Decl. ¶ 2, Ex. 15 at 3M00003711-14.) In the first Office Action, the Patent
`
`Office examiner required 3M to restrict the application to either the product claims or the
`
`method claims. (Id. ¶ 2, Ex. 16 at 3M00003728.) Specifically, the examiner explained:
`
`The inventions are distinct, each from the other because of the
`following reasons: Inventions Group I [the product claims] and Group II
`[the method claims] are related as process of making and product made.
`The inventions are distinct if either or both of the following can be shown:
`(1) that the process as claimed can be used to make other and materially
`different product or (2) that the product as claimed can be made by another
`and materially different process. In the instant case, the product can be
`made by a materially different process, such as blending a thermal stabilizer
`with the propylene pellets before the extrusion step.
`
`
`. . .
`
`
`Because these inventions are distinct . . . and have acquired a
`separate status in the art as shown by their different classification,
`restriction for examination purposes as indicated is proper.
`
`
`(Id. (citations omitted).)
`
`The examiner also rejected the claims as unpatentable over the acoustical
`
`insulating webs discussed in the Thompson Patent:
`
`Thompson teaches an acoustical insulating web comprising
`microfibers having fiber diameter less than about 15 microns, a thickness of
`at least 0.5 cm, a density of less than about 50 kg/m3, and a pressure drop of
`at least about 1 mm water at a flow rate of about 32 liters/min. . . . The
`fiber-forming material may be propropylene. Webs of melt-blown
`microfibers may also contain staple fibers such as crimped bulking fibers.
`The ratio of melt-blown microfibers to crimped bulking fibers is in the
`range of about 40:60 to 95:5. The invention may also contain microfiber
`microwebs. Fiber can also contain various additives including antioxidants.
`
`
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`(Id. at 3M00003730-31 (citations omitted).) The examiner further explained:
`
`
`The difference between what is taught by Thompson and that presently
`claimed is that Thompson does not disclose the amount of antioxidants in his
`insulation to achieve the presently claimed thermal stability.
`
`It would have been obvious for one of ordinary skill in the art to have
`modified the amount of antioxidant to achieve the thermal stability presently
`claimed. One of ordinary skill in the art would have been motivated to do this in
`order to provide an acoustic insulation web which is more or less thermally stable.
`Further, it has been held that the routine varying of parameters to produce
`expected changes are within the ability of one of ordinary skill in the art.
`Patentability over the prior art will occur only if the parameter variation produces
`an unexpected result. . . .
`
`
`(Id. at 3M00003731.)
`
`
`
`In response to this Office Action, 3M elected to pursue the product claims,
`
`amending claim 1 as follows:
`
`A thermally stable acoustical insulation microfiber web for
`attenuation of sound waves comprising a melt-blown polypropylene
`microfiber web having an average effective fiber diameter of less than
`about 15 microns, a thickness of at least about 0.5 cm, a density of less than
`50 kg/m3 and a pressure drop of at least about 1 mm water at a flow rate of
`about 32 liters/min., said polypropylene microfibers formed of
`polypropylene homopolymers, copolymers or blends thereof with a
`nonvolatile thermal stabilizer or antioxidant is uniformly distributed
`throughout the microfibers such that the [which] microfibers are thermally
`stable for at least 10 days at 135° C.
`
`(Id. ¶ 2, Ex. 17 at 3M00003740 (emphasis in original).) 3M also explained:
`
`Although Thompson et al. generically lists antioxidants among many
`other potential additive materials that can be incorporated into the vast
`range of fibrous webs described, Thompson et al. does not indicate the
`manner in which antioxidants can be incorporated. However, typically
`antioxidants can be either sprayed onto the surface of fibrous materials, or
`sometimes can be incorporated into the melt phase prior to forming the
`fibers.
`
`Typical topical fiber spraying is relatively easy to accomplish but
`was found not be effective relative to melt flown polypropylene webs used
`
`
`
`14
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`PGR2020-00056 U.S. Patent No. 10,422,617
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`as acoustical insulation. However, with melt blown microfibers
`incorporating an antioxidant or thermal stabilizer into the melt phase of
`webs is problematic. The addition of an antioxidant and/or thermal
`stabilizer directly into the melt is not a conventional variable in order to
`vary performance of the melt blown formed fiber webs as suggested by the
`Examiner. . . . In forming melt-blown microfibers, the polymers used are
`conventionally exposed to extremely high temperatures, which high
`temperatures are often intentionally used to thermally degrade
`polypropylene to enable the formation of uniform melt-blown fibers. . . .
`With this in mind, the addition of significant levels of thermal stabilizers
`and/or antioxidants directly into the polypropylene melt phase prior to
`forming melt-blown microfibers is not a simple procedure or conventional
`in any sense.
`Initially, most antioxidants or thermal stabilizers are sacrificial in
`nature and it would be expected that the high temperatures employed
`during the melt-blown processing of polypropylene would use up or destroy
`most additive antioxidants or thermal stabilizers in the melt. Furthermore,
`even if added, it would be expected that the antioxidants or stabilizers could
`substantially interfere with the controlled degradation of the polypropylene
`materials during melt processing prior to fiber formation.
`The invention teaches that the conflicting needs of providing a
`uniformly distributed quantity of thermal stabilizer or antioxidant in the
`fibers forming the acoustical insulation coupled with the need for
`controllably degrading the polypropylene prior to formation of the
`melt-blown microfibers can be reconciled by injecting an antioxidant or
`thermal stabilizer as a liquid st[r]eam into a conveying tube equipped with
`an injection port located between the die in which the fibers are formed and
`the extruder in which the polypropylene is controllably melted and
`degraded . . . .
`
`(Id. at 3M00003742-44.) 3M also explained that adding high levels of antioxidants to the
`
`melt phase “is not a conventional result effective variable in the melt blown art as
`
`suggested by the Examiner. The art as a whole, in fact, would teach away from this
`
`approach.” (Id. at 3M00003744.)
`
`The examiner issued a Notice of Allowability, explaining:
`
`Applicant’s arguments . . . are persuasive and are incorporated
`herein as reasons for allowance. Specifically, while Thompson [] teaches
`the basic structure of the claimed invention, there is no suggestion to add a
`
`15
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`Apex Tool Group, LLC v. Milwaukee Electric Tool Corporation
`PGR2020-00056 U.S. Patent No. 10,422,617
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`

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`nonvolatile thermal stabilizer or antioxidant uniformly throughout the
`microfibers such that microfibers are thermally stable for at least 10 days at
`135°C. Thompson merely lists antioxidants as an additive among many
`other potential additive materials that can be incorporated into the vast
`range of fibrous webs and does not teach a method by which the claimed
`thermal stability can be achieved. When all the limitations of the claims are
`considered as a whole, the claims are patentable over the prior art.
`
`
`(Id. ¶ 2, Ex. 18 at 3M00003749 (emphasis added).) The ’375 Patent was issued on
`
`June 30, 1998. 3M pursued a separate patent that was directed at a method of making
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`thermally stable acoustical insulation that included the step of homogeneously blending
`
`the antioxidant into the feedstream after extrusion. (Id. ¶ 2, Ex. 19 at [54] & c. 12,
`
`ll:7-32.)
`
`B.
`
`Disputed Claims
`
`1.
`
`“pressure drop”
`
`The parties dispute the meaning of the term “a pressure drop of at least about
`
`
`
`1 mm water at a flow rate of about 32 liters/min.” as it appears in claims 1, 7-11, and 17
`
`of the ’375 Patent. (’375 Patent at c. 11, ll:42-44.)
`
`
`
`This claim term relates to the amount of force per unit area required for a volume
`
`of air to pass through a given sample in a given period of time. (Osswald Decl. ¶ 40.)
`
`Pressure drop is a measured characteristic of acoustical insulation because a greater
`
`pressure drop (i.e., force required for air to pass through a sample) correlates to greater
`
`sound attenuation. (Id.)
`
`
`
`Defendants submit that the term “pressure drop” is indefinite because: (1) the
`
`measured pressure drop depends upon the face v