United States Court of Appeals 

for the Federal Circuit ______________________

E.I. DU PONT DE NEMOURS & COMPANY,

Plaintiff-Appellee

v.

UNIFRAX I LLC,

Defendant-Appellant

______________________

2017-2575

______________________

Appeal from the United States District Court for the 

District of Delaware in No. 1:14-cv-01250-RGA, Judge 

Richard G. Andrews.

______________________

Decided: April 17, 2019

______________________

CHRISTOPHER LANDGRAFF, Bartlit Beck LLP, Chicago, 

IL, argued for plaintiff-appellee. Also represented by 

SHARON DESH, MARK LESLIE LEVINE. 

 JACOB M. HOLDREITH, Robins Kaplan LLP, Minneapolis, MN, argued for defendant-appellant. Also represented by BRENDA L. JOLY, DAVID ALLEN PRANGE. 

 ______________________

Before O’MALLEY, REYNA, and HUGHES, Circuit Judges.
2 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

Opinion for the court filed by Circuit Judge REYNA.

Dissenting opinion filed by Circuit Judge O’MALLEY.

REYNA, Circuit Judge.

This appeal arises from a patent infringement suit filed 

in the U.S. District Court for the District of Delaware. Defendant-Appellant Unifrax I LLC appeals from the district 

court’s claim construction and denial of its motions for 

judgment of non-infringement and invalidity as a matter of 

law after a jury found that Unifrax I LLC’s flame barrier 

product infringed the asserted patent and that Unifrax I 

LLC failed to prove the asserted patent was invalid. Because the district court correctly construed “100% by 

weight” and substantial evidence supports the jury’s verdict, we affirm. 

BACKGROUND

I. The Asserted Patent

U.S. Patent No. 8,607,926 (“the ’926 patent”), entitled 

“Composite Flame Barrier Laminate for a Thermal and 

Acoustic Insulation Blanket,” issued on December 17, 

2013. The ’926 patent claims composite laminates that are 

incorporated into thermal-acoustic blankets installed on 

the interior of the fuselage in aircraft to shield passengers 

from flames and reduce noise. The laminates claimed in 

the ’926 patent have three layers of materials: (1) a polymeric film layer; (2) an inorganic refractory layer; and (3)

an adhesive layer between the film and refractory layer. 

’926 patent col. 1 ll. 48–51; col. 9, ll. 6–17 (claim 1); Fig. 1. 

The ’926 patent lists Drs. Llewellyn Bentley (“Ley”) Richardson, III, and Darisuz Wlodzimierz Kawka of E.I. du

Pont de Nemours & Company (“DuPont”) as inventors. 

The application that led to the ’926 patent was filed on 

December 14, 2011, as a continuation-in-part of the application that led to U.S. Patent No. 8,292,027 (“the ’027 patent”). The parent ’027 patent claims a polymeric film layer 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 3

and an inorganic refractory layer but not an adhesive layer. 

The ’027 patent also names Dr. Richardson as an inventor 

but does not name Dr. Kawka.

The primary dispute in this case concerns the “inorganic refractory layer,” which generally consists of “vermiculite platelets” that come from the natural mineral 

vermiculite. Claim 1 of the ’926 patent—the only independent claim at issue—recites the following:

1. A multilayer laminate for use as a flame barrier 

layer for an aircraft comprising in order (i) a polymeric film layer capable of withstanding a temperature of at least 200 C for at least 10 min[;]

(ii) an adhesive layer having an areal 

weight of from 2 to 40 gsm capable of 

activation at a temperature of from 75 

to 200 degrees C[;] and

(iii) an inorganic refractory layer;

wherein the inorganic refractory layer 

of (iii) comprises platelets in an amount 

of 100% by weight with a dry areal 

weight of 15 to 50 gsm and a residual 

moisture content of no greater than 10 

percent by weight.

Id. col. 9 ll. 6–17 (emphasis added). The three layers comprising the claimed multilayer laminate are depicted in the 

’926 patent in Figure 1:

E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 5

The jury found that the Combi-Film 3G11 product infringes the ’926 patent and that the asserted claims were

not invalid. Unifrax moved for judgment of non-infringement and invalidity as a matter of law. The court denied 

Unifrax’s motions, finding that legally sufficient evidence 

supported the jury’s verdicts of infringement and no anticipation or obviousness. J.A. 41–43. 

A central issue in this appeal is the court’s construction 

of the term in claim 1, “100% by weight.” During claim 

construction proceedings, DuPont proposed that “100% by 

weight” means “[t]here is no carrier material such as resin, 

adhesive, cloth or paper in addition to the inorganic platelets. There may be some residual dispersant arising from 

incomplete drying of the platelet dispersion.” E.I. du Pont 

de Nemours & Co. v. Unifrax I LLC, No. 1:14-CV-1250, 

2016 WL 158031, at *5–6 (D. Del. Jan. 13, 2016) (“Claim 

Construction Order”). Unifrax proposed that “100% by 

weight” be given its “[p]lain meaning—no construction is 

necessary.” Id. According to the district court, “the parties’ 

dispute boils down to whether the platelets are 100% of the 

inorganic refractory layer or 100% relative to carrier material in the inorganic refractory layer.” Id. at *6.

The district court adopted DuPont’s proposed construction. In reaching its conclusion, the district court cited the 

’926 patent’s specification, which states:

The refractory layer comprises platelets. Preferably at least 85% of the layer comprises platelets, 

more preferably at least 90% and most preferably 

at least 95%. In some embodiments, platelets comprise 100% of the layer. The refractory layer may 

comprise some residual dispersant arising from incomplete drying of the platelet dispersion during 

manufacture.

’926 patent col. 3 ll. 21–26. The district court stated that 

“[t]he grammatical and most natural reading of this passage is that ‘[t]he refractory layer may comprise residual
6 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

dispersant’ refers to all the embodiments mentioned in the 

paragraph, including the embodiment in which platelets 

comprise 100% of the layer.” Claim Construction Order, 

2016 WL 158031, at *7. Therefore, the specification supported a construction of “100% by weight” permitting some 

residual dispersant. 

The district court also looked to the specification of the 

parent ’027 patent, which it considered as intrinsic evidence, that states “[i]n one embodiment of this invention, 

the inorganic platelet layer contains 100% platelets, i.e. 

there is no carrier material such as resin, adhesive, cloth 

or paper. However, there may be some residual dispersant 

arising from incomplete drying of the platelet dispersion.” 

’027 patent col. 2 ll. 32–36. The district court noted that, 

although the ’027 patent and the ’926 patent did not share 

the disputed “100%” claim term, both patents “claim inventions that comprise a layer that comprises platelets” and 

the ’027 patent “illuminate[s] the meaning of ‘100%’ as it 

pertains to such a layer because the “statement relates to 

common subject matter.” Claim Construction Order, 2016 

WL 158031, at *8. The district court concluded that the 

intrinsic evidence supports the construction that “100% by 

weight” platelets refers to “the quantity of platelets relative to carrier material,” which allows for residual dispersant in the inorganic refractory layer. Id. at *9. 

The district court also considered whether during prosecution of the ’926 patent, the patentees disclaimed refractory layers that contain less than 100% by weight platelets 

to overcome a rejection in view of the prior art—U.S. Patent No. 6,670,291 (“Tompkins”). The examiner rejected 

the application that led to the ’926 patent over Tompkins 

because Tompkins taught a refractory layer with a platelet 

concentration of less than 100%. Id. The patentees

amended the claim to add language reciting that the inorganic refractory layer comprises platelets in the amount of 

“100% by weight.” Id. According to the district court, 

DuPont did not dispute that this resulted in disclaimer of 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 7

at least “embodiments comprising an inorganic refractory 

layer containing platelets in an amount less than 100% by 

weight.” Id. 

The district court further considered whether the patentees disclaimed inorganic refractory layers that contained residual dispersant. Noting that the amended 

language recited “platelets in the amount of 100% by 

weight . . . and a residual moisture content,” the district 

court found that the patentees had not disclaimed “refractory layers that contain anything at all other than platelets” and that the disclaimer had no effect on the 

permissibility of non-carrier materials such as residual dispersants or moisture in the refractory layer. Id. In the 

district court’s view, the disclaimer limited the scope of the 

claimed layers to those containing no carrier material such 

as a resin or an adhesive. Id. 

III. The Accused Product

Unifrax produces the accused Combi-Film 3G11 product. The “vermiculite coating” layer shown in the figure 

below1 is the layer that DuPont contends meets the claimed 

“inorganic refractory layer” limitation in this appeal.

 

1 Despite the visible “Unifrax Confidential” designation, this figure appears in DuPont’s non-confidential response brief.
8 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

Appellee Br. 10; J.A. 8033. The refractory layer in CombiFilm 3G11 consists of an HTS-SE vermiculite dispersion 

containing vermiculite, a material known as DEHESIVE 

480, tetrasodium pyrophosphate, and water.

DISCUSSION

We review the district court’s ultimate determination 

on claim construction de novo, while any underlying factual 

findings related to extrinsic evidence are reviewed for clear

error. CardSoft, LLC v. VeriFone, Inc., 807 F.3d 1346, 

1348, 1349–50 (Fed. Cir. 2015). 

Review of the district court’s denial of judgment as a 

matter of law is governed by the law of the regional circuit, 

here the Third Circuit. See Transocean Offshore Deepwater 

Drilling, Inc. v. Maersk Drilling USA, Inc., 699 F.3d 1340, 

1346–47 (Fed. Cir. 2012). The Third Circuit reviews de 

novo a district court’s ruling on a motion for judgment as 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 9

matter of law. Intellectual Ventures I LLC v. Motorola Mobility LLC, 870 F.3d 1320, 1324 (Fed. Cir. 2017); McKenna 

v. City of Philadelphia, 582 F.3d 447, 460 (3d Cir. 2009). 

Judgment as matter of law is appropriate if “the court 

finds that a reasonable jury would not have a legally sufficient evidentiary basis to find for [a] party.” Fed. R. Civ. 

P. 50(a)(1). Judgment as a matter of law is “sparingly invoked” and “granted only if, viewing the evidence in the 

light most favorable to the nonmovant and giving it the advantage of every fair and reasonable inference, there is insufficient evidence from which a jury reasonably could 

find” for the nonmovant. Marra v. Phila. Hous. Auth., 497 

F.3d 286, 300 (3d Cir. 2007) (internal quotation marks 

omitted). “The question is not whether there is literally no 

evidence supporting the party against whom the motion is 

directed but whether there is evidence upon which the jury 

could properly find a verdict for that party.” Becton, Dickinson & Co. v. Tyco Healthcare Grp., LP, 616 F.3d 1249, 

1253 (Fed. Cir. 2010) (quoting Lightning Lube, Inc. v. Witco 

Corp., 4 F.3d 1153, 1166 (3d Cir. 1993)). 

Infringement is a question of fact, reviewed for substantial evidence when tried to a jury. ACCO Brands, Inc. 

v. ABA Locks Mfrs. Co., 501 F.3d 1307, 1311 (Fed. Cir. 

2007). Similarly, anticipation under 35 U.S.C. § 102 is a 

question of fact, reviewed for substantial evidence when 

tried to a jury. TI Grp. Auto. Sys. (N. Am.), Inc. v. VDO N. 

Am., L.L.C., 375 F.3d 1126, 1133 (Fed. Cir. 2004). “Priority, conception, and reduction to practice are questions of 

law which are based on subsidiary factual findings.” 

Cooper v. Goldfarb, 154 F.3d 1321, 1327 (Fed. Cir. 1998). 

We have treated the question of whether inventor testimony asserting priority is sufficiently corroborated as a 

question of fact. See NFC Tech., LLC v. Matal, 871 F.3d 

1367, 1371 (Fed. Cir. 2017) (citing Fleming v. Escort Inc., 

774 F.3d 1371, 1377 (Fed. Cir. 2014)).
10 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

I. Claim Construction

We review the district court’s ultimate determination 

on claim construction de novo. CardSoft, 807 F.3d at 1349–

50. The parties dispute whether the district court correctly 

construed the claim term “100% by weight.” The first step 

in the patent infringement analysis requires the court to 

construe the scope and meaning of the asserted claims. See 

Markman v. Westview Instruments, Inc., 517 U.S. 370, 

372–74 (1996). The purpose of claim construction is to give 

meaning to the claim terms according to how a person of 

ordinary skill in the art would have understood them at the 

time of the invention in light of the entire patent, including 

the claims in which the terms appear and the specification. 

Phillips v. AWH Corp., 415 F.3d 1303, 1312–14 (Fed. Cir. 

2005) (en banc). “We cannot look at the ordinary meaning 

of [a] term . . . in a vacuum” but must consider “the context 

of the written description and the prosecution history.” 

Medrad, Inc. v. MRI Devices Corp., 401 F.3d 1313, 1319 

(Fed. Cir. 2005). “When the specification ‘makes clear that 

the invention does not include a particular feature, that 

feature is deemed to be outside the reach of the claims of 

the patent, even though the language of the claims, read 

without reference to the specification, might be considered 

broad enough to encompass the feature in question.’” Microsoft Corp. v. Multi-Tech Sys., Inc., 357 F.3d 1340, 1347 

(Fed. Cir. 2004) (quoting SciMed Life Sys., Inc. v. Advanced 

Cardiovascular Sys., Inc., 242 F.3d 1337, 1341 (Fed. Cir.

2001)).

Although the court may consider extrinsic evidence, 

“[i]t is well-settled that, in interpreting an asserted claim, 

the court should look first to the intrinsic evidence of record.” Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 

1582 (Fed. Cir. 1996). We have designated the prosecution 

history as part of the intrinsic evidence, including “the 

prior art cited during the examination of the patent.” Phillips, 415 F.3d at 1317; Powell v. Home Depot U.S.A., Inc., 

663 F.3d 1221, 1230–31 (Fed. Cir. 2011). The prosecution 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 11

history “contains the entire record of the proceedings in the 

Patent Office from the first application papers to the issued 

patent.” Autogiro Co. of Am. v. United States, 384 F.2d 391, 

398 (Ct. Cl. 1967); see also Phillips, 415 F.3d at 1317.

Unifrax argues that the “100% by weight” term does 

not allow for any amount of organic additives in the refractory layer. According to Unifrax, “‘100%’ means one hundred percent.” Appellant Br. 35. We must consider 

whether the context of the entire patent and other intrinsic 

evidence supports such an interpretation. We hold that it 

does not.

We begin our analysis with the claim language itself. 

Claim 1 of the ’926 patent recites that “the inorganic refractory layer of (iii) comprises platelets in an amount of 

100% by weight with a dry areal weight of 15 to 50 gsm and 

a residual moisture content of no greater than 10 percent 

by weight.” ’926 patent col. 9 ll. 14–17. That claim 1 recites 

a residual moisture content of up to “[10%] by weight” in 

addition to “100% by weight” platelets in the refractory 

layer undercuts Unifrax’s plain meaning argument that 

“‘100%’ means one hundred percent.” Unifrax’s position 

would require that the term “100% by weight” be considered alone, without reference to the surrounding claim language. The claim’s reference to both “100% by weight”

platelets and 10% residual moisture, however, supports the 

conclusion that “100% by weight” is relative to carrier material. It would be nonsensical if the total percentage of 

components comprising the inorganic refractory layer exceeded 100%. As the district court noted, this claim language does not suggest that “100%” excludes all refractory 

layers containing “anything at all other than platelets”

from the claim scope. Claim Construction Order, 2016 WL 

158031, at *9.

We next look at the specification. The specification provides that “[t]he refractory layer comprises platelets. Preferably at least 85% of the layer comprises platelets, more 
12 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

preferably at least 90% and most preferably at least 95%. 

In some embodiments, platelets comprise 100% of the 

layer. The refractory layer may comprise some residual 

dispersant.” ’926 patent col. 3 ll. 21–25. This language 

supports the district court’s conclusion that the disclosed

embodiments, including the 100% platelet embodiment, all 

allow for some amount of residual dispersant. Like the language of claim 1, this passage further supports that “100% 

by weight” is relative to carrier material in the refractory 

layer.

Unifrax contends that all twenty-four examples of the 

refractory layer in the laminates shown in the specification 

have 100% by weight inorganic platelets with no residual 

dispersant. Appellant Br. 5. Indeed, the specification 

states that all laminate examples are based on the use of a

single commercial vermiculite product known as MicroLite 963 for the refractory layer that has 0% organic material. ’926 patent col. 4 ll. 62–67; J.A. 7617–20. But the ’926

patent also lists other “suitable materials” (e.g., MicroLite 

HTS-XE) that contain a residual dispersant, and thus, less 

than 100% inorganic material, for the refractory layer. ’926

patent col. 3 ll. 47–50; J.A. 7617–26 (stating that MicroLite 

HTS-XE may contain organic additives). 

Unifrax also argues that the district court erred by 

treating the ’027 patent’s specification as intrinsic evidence 

in construing “100% by weight.” We disagree. This court’s 

precedent supports treating the specification of the ’027 patent as intrinsic evidence in construing claims in the ’926 

patent, which issued from a continuation-in-part of the application for the ’027 patent, because “the subject matter is 

common to the continuation-in-part application.” Wang

Labs., Inc. v. Am. Online, Inc., 197 F.3d 1377, 1384 (Fed. 

Cir. 1999) (applying statements from prosecution of a parent application where subject matter was common to the 

continuation-in-part application); see also Jonsson v. Stanley Works, 903 F.2d 812, 818 (Fed. Cir. 1990) (affirming 

claim construction relying on “arguments and remarks”
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 13

made during the prosecution of a parent application for 

claim terms in a patent resulting from a continuation-inpart application despite recognizing the claims used different language). 

The district court’s construction of “100% by weight”

comes directly from language in the parent ’027 patent and 

its application:

In one embodiment of this invention, the inorganic platelet layer contains 100% platelets i.e. 

there is no carrier material such as resin, adhesive, 

cloth or paper. However, there may be some residual dispersant arising from incomplete drying of 

the platelet dispersion.

’027 patent col. 2 ll. 32–36. We agree with the district court 

that this passage relates to common subject matter and informs the meaning of the “100% by weight” claim term as 

it is used in the ’926 patent by clarifying what is not included in the refractory layer—a carrier material such as 

resin, adhesive, cloth, or paper. 

Unifrax cites Advanced Cardiovascular Systems, Inc. v. 

Medtronic, Inc., 265 F.3d 1294, 1305–06 (Fed. Cir. 2001),

to assert that considering the ’027 patent specification was 

improper. Advanced Cardiovascular provides one example 

of circumstances when it is plainly appropriate to treat a 

parent application as intrinsic evidence: when considering

two related patents with identical claim terms. Id. (“The 

prosecution history of a related patent can be relevant if, 

for example, it addresses a limitation in common with the 

patent in suit.”). We do not read Advanced Cardiovascular

to create a strict requirement that to consider a parent patent as intrinsic evidence, the exact claim term at issue in 

the child patent must appear in the parent patent’s claims. 

Id. In Advanced Cardiovascular, we declined to import a 

limitation into the child patent claims based on the prosecution history of the parent application where “[t]he patentee’s whole point in filing the [child application] was to 
14 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

secure broader claims” by removing a claim term. Id. 

Thus, Advanced Cardiovascular concerned the “absence of 

a claim term[,]” not merely “no common claim terms in dispute.” Id. That is not the case here. 

Other cases set forth additional circumstances where 

familial patents inform the construction of a claim term

and are appropriately treated as intrinsic evidence. When 

a parent application includes statements involving “common subject matter” with the terms at issue, those statements are relevant to construction of the terms in the child 

patent. See Wang Labs, 197 F.3d at 1384; Jonsson 903 F.2d 

at 818; see also, e.g., Ormco Corp. v. Align Tech., Inc., 498 

F.3d 1307, 1314 (Fed. Cir. 2007). Such is the case in this 

action. 

The ’027 and ’926 patents have a familial relationship: 

the ’926 patent issued from a continuation-in-part of the 

application that issued as the ’027 patent. See ’926 patent 

col. 1 ll. 5–8; id., Related U.S. Application Data. Accordingly, as a continuation-in-part, the ’926 patent “disclos[es] 

all or a substantial part of the subject-matter of the prior 

application,” i.e., the application that led to the ’027 patent. 

U.S. Water Servs., Inc. v. Novozymes A/S, 843 F.3d 1345, 

1348 n.1 (Fed. Cir. 2016). In addition to the familial relationship, the application that led to the ’027 patent is listed 

on the face of the ’926 patent as a prior art reference cited 

during prosecution. ’926 patent, References Cited.

Both patents claim composite laminates that are used 

as flame barriers comprised of a polymeric film layer and 

an inorganic refractory layer that itself comprises platelets. Both specifications disclose 100% platelet refractory 

layer embodiments that also allow for “residual dispersant” 

in the 100% platelet layer. Given the familial relationship, 

citation during prosecution, and common subject matter, 

the district court’s treatment of the ’027 patent as intrinsic 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 15

evidence2 was consistent with our precedent. See Wang 

Labs, 197 F.3d at 1384; Powell, 663 F.3d at 1230–31. 

We also find it persuasive that the patentees did not 

delete the definition of “100% platelet” from the ’027 patent 

specification and substantially copy the remaining language into the ’926 patent specification. Had they done so, 

one could reasonably infer that they intended to change the 

meaning of “100%” in the ’926 patent specification. But as 

the district court correctly observed, the “patentees wrote 

a new specification for the ’926 patent, drawing from the 

’027 patent more in substance than in language.” Claim 

Construction Order, 2016 WL 158031, at *8. The patentees

demonstrated in the ’926 patent the same understanding 

of 100% that we set forth here; it is relative to certain other 

materials in an embodiment where “platelets comprise 

100% of the layer” while also comprising “residual dispersant.” The revised language of the ’926 patent omits only 

the clarification that the 100% platelet layer contains “no 

carrier material.” The ’027 patent explicitly clarified that 

a dispersant and a carrier are distinct. 

The language in the ’926 patent specification is consistent with the understanding of the 100% platelet layer 

described in the ’027 patent specification. As such, there is 

no reason to infer that the patentees intended to change 

 

2 The dissent implies that statements in a parent patent’s specification may somehow have less relevance than 

“certain statements made during the prosecution history” 

for the claim construction of a child patent. Dissent Op. 9–

10. The prosecution history of the parent patent, here the

’027 patent, however, encompasses its “first application papers” to the “issued patent,” including the specification. 

Autogiro Co. of Am., 384 F.2d at 398. Thus, statements in 

the issued ’027 patent have no less relevance than other 

statements in its prosecution history in construing the 

claims of the child patent, here the ’926 patent. 
16 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

the meaning of the term or that a person of ordinary skill 

in the art would understand “100%” differently in the context of the ’926 patent. Thus, the ’027 patent specification 

illuminates the meaning of “100% by weight” to a person of 

ordinary skill in the art, who would understand that the 

term is used in the same way in the ’926 patent, relative to 

carrier material, and that while the claimed “100% by 

weight” platelet refractory layer may comprise residual 

dispersant, “there is no carrier material.”

Next, we must consider the ’926 patent’s prosecution 

history to determine whether the patentees “limited the invention in the course of prosecution, making the claim 

scope narrower than it would otherwise be.” Phillips, 415 

F.3d at 1317. Unifrax argues that the patentees disclaimed 

a refractory layer with any other material at all, including 

residual dispersants, to overcome the rejection based on 

Tompkins. DuPont does not dispute that the patentees disclaimed refractory layers comprising less than “100% by 

weight” platelets but contends that the disclaimer did not 

exclude refractory layers containing residual dispersant

from the scope of the claim. J.A. 25. The question is

whether, to get around Tompkins, the patentees’ disclaimer went so far as to also exclude embodiments with a 

refractory layer containing any non-carrier materials such 

as a residual dispersant. See Chimie v. PPG Indus., 

Inc., 402 F.3d 1371, 1384 (Fed. Cir. 2005). It did not. 

During prosecution of the application for the ’926 patent, DuPont argued that the Tompkins reference cited by 

the examiner disclosed a laminate with a 70% by weight

platelet concentration secured to a fiber carrier (i.e., the 

“second layer”). J.A. 373; J.A. 525 col. 7 ll. 6–9; J.A. 528 

col. 14 ll. 20–24. The patentees amended the claim language and explained that they had found a solution with a 

platelet concentration of 100% platelets, not requiring a 

carrier, while also clarifying that the refractory layer required “a defined areal weight and a defined residual moisture content.” J.A. 372–73 (emphasis added). The 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 17

patentees overcame the deficiency in Tompkins where

more platelets made the refractory layer too brittle or too 

heavy. Id. In adding a platelet percentage term to the 

claim language to overcome the rejection based on the 

platelet percentage disclosed in Tompkins, the ’926 patentees understood the claimed percentage as relative to carrier material in the same way that Tompkins used the 

term. That the ’926 patent specification identifies Tompkins as one of only two references in the Background of the 

Invention section further suggests that the patentees had 

the same understanding of the platelet percentage terms.

See ’926 patent col. 1 l. 22. Thus, the patentees’ amendment does not disclaim embodiments with a refractory 

layer containing moisture from “dispersant arising from incomplete drying of the platelet dispersion,” i.e., non-carrier

materials. Id. col. 3 ll. 21–26. 

The dissent concludes that “100% by weight” permits 

residual moisture but no other ingredients (such as a dispersant). Dissent Op. 7. This conclusion contradicts the

undisputed fact that the accused Unifrax vermiculite layer 

contains a dispersant, tetrasodium pyrophosphate 

(“TSPP”). Appellant Br. 15 n.2. (“The specific function of 

TSPP is to be a dispersant.”) Unifrax has never contended 

the presence of TSPP avoids infringement, even under the 

plain meaning of “100% by weight.” See id. at 46–47 (arguing instead that Combi-Film 3G11 does not infringe under 

the plain meaning of “100% by weight” because of the presence of an organosilicon material, polydimethylsiloxane); 

J.A. 6016 (“Q. Now, you mentioned that there are the two 

additives in the Unifrax vermiculite layer, TSPP and 

dehesive 480. Is there any dispute about what TSPP is? A. 

No, sir. Q. Okay. Is that a dispersant? A. It is a dispersant, 

sir.”). Thus, Unifrax’s own arguments oppose the dissent’s

conclusion. 

Further, the history of this case and statements made 

by Unifrax during claim construction belie the dissent’s assertions that “[t]here is no ambiguity in [the claim]
18 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

language” and “[t]here is perhaps no clearer or simpler way 

the patentee could have conveyed such a requirement.” 

Dissent Op. 2. At claim construction, Unifrax argued that

the claim language was indefinite because “[n]othing in the 

specification or the claims informs one how the inorganic 

refractory layer may contain 100% by weight platelets and 

also include additional amounts of material to exceed 100% 

by weight . . . to accommodate some percentage of other 

content.” J.A. 797–98. Thus, Unifrax previously argued 

that the claim language contained unresolvable ambiguities, contrary to the dissent’s assertions. 

We discern no error in the district court’s construction 

of “100% by weight” to mean “[t]here is no carrier material 

such as resin, adhesive, cloth, or paper in addition to the 

inorganic platelets. There may be some residual dispersant arising from incomplete drying of the platelet dispersion.”

II. Infringement

We review the jury’s infringement verdict for substantial evidence. ACCO Brands, 501 F.3d at 1311. An infringement analysis requires a comparison of the claims to 

the accused device. Mas-Hamilton Grp. v. LaGard, Inc., 

156 F.3d 1206, 1211 (Fed. Cir. 1998). For literal infringement, the patentee must prove that the accused product 

meets all the limitations of the asserted claims; if even one 

limitation is not met, there is no literal infringement. Id. 

Unifrax argues that the district court erred in denying 

judgment of non-infringement as a matter of law because 

DuPont did not prove that Combi-Film 3G11 met the 

“platelets in an amount of 100% by weight” claim limitation 

by showing the absence of a carrier material such as an adhesive or resin in the refractory layer. Unifrax makes two 

alternative non-infringement arguments. First, Unifrax 

argues that the 5% polydimethylsiloxane (“PDMS”) in 

Combi-Film 3G11 functions as an adhesive. Second, 

Unifrax argues that silane—another material present in 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 19

Combi-Film 3G11—is a carrier material in the refractory 

layer. 

Unifrax’s non-infringement arguments rely on the 

premises that the DEHESIVE 480 material (which is comprised of PDMS) used in Combi-Film 3G11 is a carrier, or

alternatively, that silane is both included in the refractory 

layer and is a carrier. If either DEHESIVE 480 or silane 

constitutes a carrier present in the refractory layer, the accused Combi-Film 3G11 does not meet all the limitations 

of the asserted claims, and there is no literal infringement. 

See Mas-Hamilton Grp., 156 F.3d at 1211. We must determine whether substantial evidence supports a jury finding

that DEHESIVE 480 is not a carrier and that silane is either not in the refractory layer or is not a carrier. 

A. DEHESIVE 480

We agree with the district court that substantial evidence supports the jury’s finding that DEHESIVE 480 is 

not a carrier. Unifrax’s expert, Dr. Nosker, testified that a 

carrier is something that helps the platelets stick together 

in the refractory layer. J.A. 6667. DuPont’s expert, Dr. 

Morgan, agreed. J.A. 6080–81. The question therefore is 

whether DEHESIVE 480 helps platelets stick together and 

thus, is a carrier. 

Unifrax points to trial testimony in support of its assertion that silicones like PDMS can serve different functions in different applications and environments depending 

on how they are formulated, including functioning as an 

adhesive. The product data sheet from the manufacturer 

of DEHESIVE 480 refers to it repeatedly as a “release coating.” J.A. 8109–11. Dr. Haber, another Unifrax expert, 

admitted that the DEHESIVE 480 product data sheet

states that it has anti-adhesive qualities. E.g., J.A. 6882. 

Dr. Nosker also admitted that the PDMS in Microlite HTSSE is sold as a dispersant, i.e., not a carrier or binder. J.A. 

6640–41. 
20 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

Both the DEHESIVE 480 product data sheet and 

DuPont’s expert testimony show that a “crosslinker” could 

be added to DEHESIVE 480 to improve adhesion, which 

could make it then act as a “carrier.” J.A. 8109–11; J.A. 

6096–98. But it is undisputed that no crosslinker is added 

to the accused Unifrax products. Thus, the jury’s conclusion that DEHESIVE 480 is not a carrier is supported by 

substantial evidence.

B. Silane

Substantial evidence also supports that silane is not in 

the refractory layer, and that silane is not a carrier. 

DuPont’s expert testified that the vermiculite plates prevent silane from impregnating the refractory layer. 

J.A. 6036–37. In Unifrax’s schematic of the accused product, Combi-Film 3G11 (shown above), silane is shown as a 

separate layer from the vermiculite layer. J.A. 8033. Another Unifrax document similarly shows silane separately

from the vermiculite layer, referring to it as the “3g coating.” J.A. 8102; see J.A. 8103. In an internal email, 

Unifrax’s manager of the Combi-Film product team called 

silane an “overlayer coating” and “not the binder.” 

J.A. 6467–68; J.A. 8482. There was also testimony that 

silane is not added until after the vermiculite is dry, and 

thus, it would not be part of the refractory layer. Additionally, Unifrax’s expert, Dr. Nosker, admitted that he had no

direct evidence that silane impregnates the vermiculite 

layer. Accordingly, there was substantial evidence to support the jury’s conclusion that silane was not part of the 

refractory layer. 

DuPont’s expert also testified that even if silane did impregnate the refractory layer, it would not be a carrier. 

J.A. 6036–37. This testimony is supported by the abovereferenced email from Unifrax’s Combi-Film team manager, stating that silane was “not the binder” in CombiFilm 3G11. Consistent with the manufacturer’s product 

data sheet for silane, Unifrax’s expert testified that it could 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 21

be used as an additive to improve binding between an organic binder and an inorganic binder. Unifrax’s expert’s 

argument that silane functioned as a binder or carrier in 

Combi-Film 3G11 assumed that the PDMS in DEHESIVE 

480 was itself the organic binder. As discussed above, 

DuPont presented substantial evidence to support the 

jury’s conclusion that the PDMS in Combi-Film 3G11 is not 

a binder. As such, we conclude that substantial evidence 

supports the jury’s conclusion that silane is not a carrier in 

Combi-Film 3G11. 

Accordingly, because the jury’s infringement verdict is 

supported by legally sufficient evidence, we affirm the district court’s denial of Unifrax’s motion for judgment of noninfringement as a matter of law. 

III. Invalidity

A. Mormont

We review the jury’s verdict on anticipation for substantial evidence. TI Grp. Auto. Sys, 375 F.3d at 1133. 

Unifrax asserts that U.S. Patent Application Publication 

No. 2003/0170418 (“Mormont”) anticipates the asserted 

claims of the ’926 patent. To prove anticipation, Unifrax 

must show that Mormont teaches each limitation of the asserted claims. See ClearValue, Inc. v. Pearl River Polymers, 

Inc., 668 F.3d 1340, 1344 (Fed. Cir. 2012). The dispute over 

anticipation by Mormont turns on whether, despite describing methyl silicone as a resin, Mormont discloses a silicon material in the refractory layer that is essentially the 

same as the PDMS in DEHESIVE 480 in the infringing 

Combi-Film 3G11 product.

Mormont discloses a fireproofing barrier laminate material for aircraft with a polymeric film, adhesive, and a 

“mica paper” layer. J.A. 8726–30. Unifrax points to Example 2 in the Mormont reference that discloses mica paper 

as a refractory layer consisting of platelets reinforced by a 

methyl silicone material such as the “resin Wacker K.” 
22 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

J.A. 8729. Wacker K (also referred to in the briefing and 

record as “Silres K”) is manufactured by Wacker, the same

company that produces the DEHESIVE 480 material comprised of PDMS in Combi-Film 3G11. J.A. 8729. Unifrax 

argues that the methyl silicone in Wacker K is the same as

the PDMS in DEHESIVE 480 in the refractory layer in 

Combi-Film 3G11. Unifrax points to its expert’s testimony 

detailing how Mormont disclosed each limitation of claim 1 

of the ’926 patent. Unifrax asserts that DuPont failed to 

rebut that testimony by not putting up its own expert on 

anticipation by Mormont. 

The Wacker K manufacturer’s product data sheet repeatedly refers to Wacker K as a “methyl silicon resin” and 

as an ideal “binder” with “high binding strength.” 

J.A. 8218. Unifrax’s expert opined that the methyl silicone 

in Mormont and the PDMS in Combi-Film 3G11 were the 

same, yet he also admitted that (1) there are different types 

of silicones that serve different functions; (2) that Wacker 

K serves as a resin in Mormont and is a different chemical 

than the DEHESIVE 480 in Combi-Film 3G11; and 

(3) Mormont requires 5% to 25% binder or resin. 

J.A. 6878–84. Unifrax’s expert also conceded that silicone 

can function as a release agent and that the Wacker data 

sheets distinguish between silicon release agents and silicone resins. In contrast to Wacker K, the product data 

sheet for DEHESIVE 480 refers to it as a release agent 

with anti-adhesive, i.e., non-binding, properties. Although 

DuPont did not call an expert to testify as to the differences

between Mormont and the asserted claims, there was substantial documentary evidence and cross-examination testimony from Unifrax’s expert for the jury to conclude that 

the silicones in Combi-Film 3G11 and Mormont were distinct and that DEHESIVE 480 was not a resin or carrier. 

Thus, substantial evidence supports the jury verdict that 

Mormont does not anticipate the asserted claims of the ’926

patent.
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 23

B. Antedating 3G7

We review subsidiary factual findings related to priority, conception, and reduction to practice, including 

whether the evidence sufficiently corroborates inventor 

testimony, for substantial evidence. See NFC Tech., LLC, 

871 F.3d at 1371; Singh v. Brake, 317 F.3d 1334, 1340 (Fed. 

Cir. 2003). Unifrax contends that its FyreWrap® CombiFilm 3G7 (“3G7”) product—a predecessor flame barrier 

product to Combi-Film 3G11—anticipates the asserted 

claims of the ’926 patent. DuPont does not dispute that 

3G7 describes each limitation of claim 1 and was known 

and in public use on May 17, 2011, before the December 

2011 filing date of the application that led to the ’926 patent. DuPont, however, argues that the inventors conceived of the invention of the ’926 patent and reduced it to 

practice prior to 3G7’s May 2011 public use date. The question is one of priority of invention. We consider whether 

DuPont presented substantial evidence to support the 

jury’s implicit finding that the asserted claims of the ’926 

patent antedated the public use of 3G7.

“[P]riority of invention ‘goes to the first party to reduce 

an invention to practice unless the other party can show 

that it was the first to conceive the invention and that it 

exercised reasonable diligence in later reducing that invention to practice.’” Mahurkar, 79 F.3d at 1577 (quoting Price 

v. Symsek, 988 F.2d 1187, 1190 (Fed. Cir. 1993)). Conception requires formation of a “definite and permanent idea 

of the complete and operative invention” in the mind of the 

inventor. Id. To establish an actual reduction to practice, 

as opposed to the constructive reduction to practice that occurs when a patent application is filed, “the inventor must 

prove that: (1) he constructed an embodiment or performed 

a process that met all the limitations [of the claim]; and 

(2) he determined that the invention would work for its intended purpose.” Cooper, 154 F.3d at 1327. 
24 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

Dr. Richardson testified that he and Dr. Kawka—the 

named inventors of the ’926 patent—conceived of a “laminate with this combination of a vermiculite layer, adhesive 

layer, and polymer film layer” in November or December 

2009 while working at DuPont. J.A. 5675. Yet an inventor’s testimony alone is insufficient to prove conception;

some corroborating evidence is required. See Price, 988 

F.2d at 1194. An inventor’s testimony on conception can be 

corroborated through several pieces of evidence, even 

though no one piece of evidence independently proves conception, and even circumstantial evidence, so long as the 

evidence supports that the “inventor’s story is credible.” 

NFC Tech, 871 F.3d at 1372. “There is no particular formula” required for corroboration, and instead, a “rule of 

reason” analysis applies to the evaluation of all pertinent 

evidence. Singh, 317 F.3d at 1341. The same requirement 

for evidence that corroborates inventor testimony on conception also applies to the reduction to practice determination. See Cooper, 154 F.3d at 1330; see also Holmwood v. 

Sugavanam, 948 F.2d 1236, 1238–39 (Fed. Cir. 1991) (stating that the court must apply a “‘rule of reason’ standard” 

and evaluate all pertinent evidence “when weighing the 

credibility of an inventor’s story” as to reduction to practice). 

In this case, the question of entitlement to a priority 

date before the May 2011 public use date for the ’926 patent 

turns on whether DuPont offered corroborating evidence 

that, when considered in its totality and applying a “rule of 

reason” analysis, supports the credibility of Dr. Richardson 

and Dr. Kawka’s story of prior invention. See NFC Tech, 

871 F.3d at 1372. We conclude that it does. 

In 2008 and 2009, Dr. Richardson was working on developing a new refractory layer for composite laminates. 

J.A. 8276–77. Dr. Richardson’s work led to the ’027 patent 

that disclosed a refractory layer comprised of vermiculite 

platelets, including MicroLite 963 and MicroLite HTS-XE. 

See e.g., ’027 patent col. 2 l. 50–col. 3 l. 6, col. 8 ll. 5–7. As 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 25

noted above, the ’027 patent claims a polymeric film layer 

and an inorganic refractory layer but not the adhesive 

layer claimed by the ’926 patent. It is against this backdrop that he began collaborating with Dr. Kawka on work 

that led to the ’926 patent. 

Emails from December 2009 reflect Dr. Richardson and

Dr. Kawka discussing plans for a new three-layer DuPont 

composite film including a polymeric film layer, a vermiculite layer, and a new adhesive layer and their efforts to 

begin developing and testing the three-layer composite 

laminate. Testimony and evidence also showed that 

DuPont began developing and testing the three-layer laminate shortly thereafter, culminating in a successful 

burnthrough test at a Federal Aviation Administration 

(“FAA”) facility in August 2010.

We next consider the specific testimony and record evidence as to each laminate layer and the claimed limitations in turn. As to the film layer, both inventors testified 

that the polymeric film layer capable of withstanding at 

least 200° C for 10 minutes claimed in the ’926 patent was 

based on known attributes of materials, such as “PEEK”

and “Tedlar,” used by DuPont in 2009 and 2010. Product 

data sheets for those materials and documents showing the 

use of those materials in August 2010 FAA testing corroborated this testimony. Internal DuPont documents reflect 

that DuPont used PEEK in the August 2010 FAA testing.

As to the adhesive layer, Dr. Kawka testified that in 

2009, he conceived of an adhesive layer between the polymeric film layer and refractory layer with the weight range 

of 2 to 40 gsm and an activation temperature range from 

75 to 200° C and that such an adhesive layer was used in 

the August 2010 FAA testing. Documentary evidence, including a 2009 email sent by Dr. Kawka describing an adhesive layer with “0.3 osy,” or approximately 10 gsm, 

corroborated Dr. Kawka’s testimony. J.A. 8291. Other documentary evidence showed DuPont developed and tested
26 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

laminates with adhesive weights between 5 gsm and 30 

gsm in 2010, including in the August 2010 FAA testing. 

Evidence also showed adhesive activation temperature 

ranges between 75 and 200° C, including a May 2010 email 

to a contractor disclosing an activation temperature of 200° 

C; another May 2010 email identifying activation temperatures across the entire claimed range; and a July 2010 

email showing that the activation temperature for the adhesive to be used in the August 2010 FAA test was within 

the claimed range. 

As to the refractory layer, Dr. Richardson testified that 

he began using 100% vermiculite films in the laminates in 

2008 and successfully tested vermiculite dispersions of MicroLite 963 and MicroLite HTS-XE by 2009. Dr. Richardson also testified that he conceived of the weight range of 

15 to 50 gsm for the inorganic refractory layer in 2009 and 

began trying to get the moisture content below 10%. Dr. 

Kawka testified that DuPont’s vermiculite films had a residual moisture content of 3% to 5%.

Dr. Richardson’s testimony about his work with MicroLite 963 and MicroLite HTS-XE was corroborated by documents related to his work on the ’027 patent and a 2010 

presentation that showed successful testing of a vermiculite refractory layer. Dr. Richardson’s testimony regarding 

the claimed weight range was corroborated by DuPont 

emails, progress reports, and an internal presentation between October 2009 and February 2010 showing the development and testing of laminates with the refractory layer 

at various weights between 17 and 53 gsm. Evidence 

showed that the August 2010 FAA testing used a vermiculite layer of 37.2 gsm. An October 2009 progress report reflects that Dr. Richardson and Dr. Kawka were working 

together on a laminate with a refractory layer using vermiculite films with the claimed 10% or less residual moisture content. 
E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC 27

Unifrax asserts that independent of the inventors’ testimony, the documentary evidence does not disclose the 

conception or reduction to practice of the exact material attribute ranges (e.g., “a dry areal weight of 15 to 50 gsm”)

claimed in the ’926 patent for the laminate components. 

But our case law does not require that evidence have a 

source independent of the inventors on every aspect of conception and reduction to practice; “such a standard is the 

antithesis of the rule of reason.” Cooper, 154 F.3d at 1331 

(quoting Knorr v. Pearson, 671 F.2d 1368, 1374 (CCPA 

1982)). Here, the law requires only that the corroborative

evidence, including circumstantial evidence, support the

credibility of the inventors’ story. NFC Tech, 871 F.3d at 

1372. 

Notably, Unifrax does not point to any evidence that 

contradicts or calls the credibility of the inventors’ testimony into question. Applying the “rule of reason” analysis, 

we conclude that the corroborative evidence supports the 

credibility of Dr. Richardson and Dr. Kawka’s story. 

The documents from 2009 and 2010 related to the refractory layer support Dr. Richardson’s testimony. For example, these documents show refractory layer weights 

between 17 and 53 gsm and support his testimony that he 

conceived of the claimed 15 to 50 gsm weight range in 2009,

and at least before May 2011. Even though no single independent document precisely shows the entire claimed 

range, these documents sufficiently support the credibility 

of his account. See Fleming v. Escort Inc., 774 F.3d 1371, 

1377 (Fed. Cir. 2014) (finding sufficient corroboration although “none of the corroborating evidence constitute[d] definitive proof of [the inventor’s] account or disclose[d] each 

claim limitation as written” because “the corroboration requirement has never been so demanding”). Documents 

also corroborated Dr. Kawka’s testimony that the 37.2 gsm 

vermiculite layer used in the August 2010 FAA testing met 

the claimed limitations for the refractory layer. For each 

aspect of the claimed limitations, other corroborating 
28 E.I. DU PONT DE NEMOURS & CO. v. UNIFRAX I LLC

evidence similarly supported the credibility of the inventors’ story of conception of the claimed ranges and reduction to practice of an embodiment meeting the limitations. 

Under the “rule of reason” analysis, the evidence in its 

totality supports the jury’s finding that the inventors’ testimony was sufficiently corroborated. Therefore, substantial evidence supports the inventors’ story of a conception 

date and reduction to practice before the May 17, 2011 public use date of 3G7, and, therefore, 3G7 is not anticipatory 

prior art. 

Accordingly, because the jury’s verdict of no-invalidity 

is supported by legally sufficient evidence, we affirm the 

district court’s denial of Unifrax’s motion for judgment of 

invalidity as a matter of law. 

CONCLUSION

We have considered Unifrax’s other arguments and 

find them unpersuasive. For the foregoing reasons, the decisions of the district court are affirmed. 

AFFIRMED

COSTS

No costs.
United States Court of Appeals 

for the Federal Circuit ______________________

E.I. DUPONT DE NEMOURS & COMPANY,

Plaintiff-Appellee

v.

UNIFRAX I LLC,

Defendant-Appellant

______________________

2017-2575

______________________

Appeal from the United States District Court for the 

District of Delaware in No. 1:14-cv-01250-RGA, Judge 

Richard G. Andrews.

______________________

O’MALLEY, Circuit Judge, dissenting.

I respectfully dissent from the majority’s ruling affirming the district court’s denial of JMOL on noninfringement. 

That ruling is predicated on an erroneous construction of 

“100% by weight” that ignores the plain meaning of “100%”

and introduces more ambiguity than it resolves. Because

this construction led the jury down the wrong path en route 

to its infringement verdict, the construction should be vacated and the noninfringement JMOL ruling reversed.

I. THE ’926 PATENT CLAIMS AND SPECIFICATION SUPPORT 

UNIFRAX’S PLAIN AND ORDINARY MEANING CONSTRUCTION

The ’926 patent claims recite “an inorganic refractory 

layer” that “comprises platelets in an amount of 100% by 
2 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

weight with a dry areal weight of 15 to 50 gsm and a residual moisture content of no greater than 10 percent by 

weight.” ’926 patent, col. 9, ll. 13–17 (emphases added).

There is no ambiguity in this language. The “platelets” 

must be present in the refractory layer “in an amount of 

100% by weight.” The “100% by weight” language, coupled 

with the requirement that the platelets exist in an “inorganic refractory layer,” clearly contemplates that the platelets—i.e., inorganic material—constitute the entirety of the 

refractory layer.1 That leaves no room for other organic 

additives. There is perhaps no clearer or simpler way the 

patentee could have conveyed such a requirement. 

See Phillips v. AWH Corp., 415 F.3d 1303, 1314 (Fed. Cir. 

2005) (en banc) (“In some cases, the ordinary meaning of 

claim language as understood by a person of skill in the art 

may be readily apparent even to lay judges, and claim construction in such cases involves little more than the application of the widely accepted meaning of commonly 

understood words.”); Takeda Pharm. Co. v. Zydus Pharm. 

USA, Inc., 743 F.3d 1359, 1363–64 (Fed. Cir. 2014) 

(“[T]here is no indication in the claim that 400 μm was intended to mean anything other than exactly 400 μm.”). 

In short, the claims “mean precisely what they say,” Cent. 

Admixture Pharmacy Servs., Inc. v. Advanced Cardiac 

Sols., P.C., 482 F.3d 1347, 1355 (Fed. Cir. 2007), and we 

should construe them accordingly.

 

1 Unifrax does not appear to dispute that “100% by 

weight” could encompass the presence of minor impurities. 

See E.I. du Pont de Nemours & Co. v. Unifrax I LLC, No. 

14-1250-RGA, 2016 WL 158031, at *6 (D. Del. Jan. 13, 

2006) (noting Unifrax’s argument that “the plain and ordinary meaning of ‘100%’ would not necessarily preclude the

presence of impurities or ‘one particle of dust, [or] one droplet of moisture, [or] one molecule of a residual dispersant’”).
E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC 3

The majority finds ambiguity in “100%” because the

claims allow the refractory layer to comprise “a residual 

moisture content of no greater than 10 percent by weight.” 

The majority suggests that, if one were to adopt the plain 

and ordinary meaning of “100% by weight,” the components of the refractory layer would add up to 110%. Majority Op. at 11 (“It would be nonsensical if the total 

percentage of components comprising the inorganic refractory layer exceeded 100%.”). But this purported ambiguity 

is easily resolved by viewing “residual moisture” in context. 

The claims refer to a “dry areal weight of 15 to 50 gsm,” 

which implies that the “100% by weight” requirement applies when the refractory layer is dry. The “residual moisture” language, by contrast, clarifies that there can be 

moisture present after the remaining steps of the manufacturing process are carried out. For example, the ’926 patent describes experiments in which the refractory layer is 

immersed in a cation-rich solution and then dried in an 

oven until the laminate contains “about 3% moisture content.” ’926 patent, col. 8, ll. 49–58 (“Once dried to about 3% 

moisture content, the cation treated material was removed 

from the oven.”).2 

 

2 Other portions of the specification confirm this understanding. For example, the specification states that the 

refractory layer can have “some residual dispersant arising 

from incomplete drying of the platelet dispersion during 

manufacture.” ’926 patent, col. 3, ll. 24–26 (emphasis 

added). The ’926 patent also states that “[v]ermiculite typically comprises by (dry) weight, on a theoretical oxide basis, about 38–46% SiO2, about 16–24% MgO, about 11–16% 

Al2O3, about 8–13% Fe2O3 and the remainder generally oxides of K, Ca, Ti, Mn, Cr, Na, and Ba.” Id. at col. 3, ll. 40–

44 (emphasis added). These passages imply that the refractory layer is a 100%-platelet composition dispersed in 
4 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

Put simply, the claim language says that the refractory 

layer initially comprises a 100%-platelet composition and 

then it also allows the refractory layer to retain up to 10% 

“residual moisture” after drying. DuPont’s counsel conceded as much before the district court. See J.A. 819 at

63:13–64:25 (The Court: “[T]he ‘100% by weight of platelets,’ is that ‘100% by weight,’ itself, 15 to 50 gsm?” 

DuPont: “Yes. The dry aerial [sic] weight.” . . . The Court: 

“And that 10% by weight is relative to what?” DuPont: “To 

the total weight of the layer when it’s not dry. . . . [T]he 

dry weight would be without the water, and the residual 

moisture is with.”).

The majority also relies on a passage in the ’926 patent’s specification referring to “residual dispersant”:

Preferably at least 85% of the layer comprises 

platelets, more preferably at least 90% and most 

preferably at least 95%. In some embodiments, 

platelets comprise 100% of the layer. The refractory layer may comprise some residual dispersant 

arising from incomplete drying of the platelet dispersion during manufacture.

’926 patent, col. 3, ll. 21–26. But this passage does not justify a construction that deviates from the plain language of 

the claim. As an initial matter, the claims recite “residual 

moisture” and not “residual dispersant.” In any event, this 

passage supports Unifrax’s reading. It suggests that the 

refractory layer should contain source material comprised 

of 100% dry platelets dispersed in water using a “dispersant,” and that, “during manufacture,” the water is dried 

(and therefore evaporated). Some “residual dispersant” 

can remain in the layer—just as residual moisture can remain—if the layer is not completely dried. Id. (permitting 

 

an aqueous solution and dried during the manufacturing 

process (leaving some residual moisture behind).
E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC 5

the refractory layer to contain residual dispersant “arising 

from incomplete drying”). But, critically, the “100% by 

weight” limitation focuses on the dried source material

(i.e., the platelets), not on the residual dispersant.

The majority asserts that a construction excluding dispersants goes further than Unifrax requests. Majority Op. 

at 17. Our task, however, is to interpret the claims based 

on their plain language in view of the intrinsic and extrinsic record. See, e.g., Exxon Chem. Patents, Inc. v. Lubrizol 

Corp., 64 F.3d 1553, 1556 (Fed. Cir. 1995) (“[T]he judge’s 

task is not to decide which of the adversaries is correct. Instead the judge must independently assess the claims, the 

specification, and if necessary the prosecution history, and 

relevant extrinsic evidence, and declare the meaning of the 

claims.”). Regardless, Unifrax argued that the ’926 patent 

claims, as amended, “claim[] embodiments where platelets 

comprise 100% of the dried layer.” Appellant’s Br. at 40; 

see also J.A. 779 (criticizing DuPont for shifting away from 

its earlier position that “its inorganic refractory layer requires 100% by weight platelets without qualification”). 

It is irrelevant that Unifrax took a different position at 

trial, where it could not challenge the district court’s construction. Compare Majority Op. at 17 (citing statements 

during trial), with O2 Micro Int’l Ltd. v. Beyond Innovation 

Tech. Co., 521 F.3d 1351, 1359 (Fed. Cir. 2008) (“When the 

claim construction is resolved pre-trial, and the patentee 

presented the same position in the Markman proceeding as 

is now pressed, a further objection to the district court’s 

pre-trial ruling may indeed have been not only futile but 

unnecessary.”).

The majority also rests its construction on the fact that 

the ’926 patent mentions MicroLite HTS-XE as a “suitable 

material[].” Majority Op. at 12. But the datasheet published by the manufacturer of MicroLite—cited by the majority—distinguishes between “unformulated” and 

“formulated” dispersions. J.A. 7617. The former category 

includes products that “are 100% inorganic, consisting only 
6 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

of vermiculite and water.” J.A. 7617. The latter, by contrast, includes products, such as MicroLite HTS-XE, with 

other “additives.” Id. That the claims recite the same language this manufacturer used to describe unformulated

dispersions—100% inorganic—implies that DuPont 

claimed those dispersions and not formulated ones. This is 

particularly salient here because the “100% by weight” language was specifically added to overcome prior art.3 And 

so, while the original claims may have been broad enough 

to encompass a refractory layer made of MicroLite HTSXE, the amended claims are not. See, e.g., Elekta Instrument S.A. v. O.U.R. Sci. Int’l, Inc., 214 F.3d 1302, 1308 

(Fed. Cir. 2000) (noting that “the unambiguous language of 

the amended claim controls over any contradictory language in the written description” even when this means the 

claims, as amended, no longer cover the “only embodiment 

disclosed in the specification”). Besides MicroLite HTSXE, the majority acknowledges that “all twenty-four 

 

3 Original claim 1 recited an “inorganic refractory 

layer” without limitation as to the layer’s composition. See 

J.A. 300. That claim was rejected over a prior art reference 

(Tompkins) that taught a refractory layer having platelets 

as the main component, up to 70% by weight. DuPont 

amended the claim by adding the “100% by weight” limitation at issue here. See J.A. 374. In so doing, DuPont distinguished Tompkins by noting that, while 

“Tompkins . . . directly require[s] a platelet concentration 

which is considerably less than 100%,” the amended claims 

recite a multilayer structure in which “the platelet concentration is 100%.” J.A. 373. At the very least, by distinguishing Tompkins based on its 70%-platelet 

concentration, DuPont disclaimed platelet concentrations

considerably less than 100%. The majority’s contrary conclusion—that the refractory layer can include dispersants 

because it has a defined moisture content—simply repeats 

its misreading of the claim language. Majority Op. at 15. 
E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC 7

[other] examples of the refractory layer . . . shown in the 

specification have 100% by weight inorganic platelets with 

no residual dispersant.” Majority Op. at 12.

For these reasons, I would conclude that a proper reading of “100% by weight” permits the refractory layer to contain residual moisture but no other ingredients.

II. THE ’027 PARENT PATENT DOES NOT JUSTIFY 

A CONTRARY CONSTRUCTION 

Rather than giving “100%” its plain and ordinary 

meaning, the majority concludes that “100% by weight” 

means 100% “relative to carrier material in the refractory 

layer.” See, e.g., Majority Op. at 12. But the ’926 patent 

does not mention “carrier material” and neither party proffered any expert testimony stating that a skilled artisan 

would read the patent as describing such material. Instead, this term comes from the specification of the ’926 patent’s parent—the ’027 patent. The specification of that

patent includes the following passage:

In one embodiment of this invention, the inorganic 

platelet layer contains 100% platelets i.e. there is no 

carrier material such as resin, adhesive, cloth or paper. However, there may be some residual dispersant arising from incomplete drying of the platelet 

dispersion.

’027 patent, col. 2, ll. 32–36 (emphasis added). Both parties 

agree—and the district court found—that this passage does 

not rise to the level of lexicography. See E.I. du Pont, 2016 

WL 158031, at *8 (“DuPont’s construction does not meet 

the exacting standards for finding lexicography.”); Appellee 

Br. 16 n.3 (DuPont agreeing that lexicography does not apply). Yet the district court’s construction imported this 

passage from the ’027 patent into the ’926 patent claims 

nearly verbatim. Majority Op. at 13 (“The district court’s 

construction of ‘100% by weight’ comes directly from language in the parent ’027 patent . . . .”). That is improper. 
8 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

See Meds. Co. v. Mylan, Inc., 853 F.3d 1296, 1306 (Fed. Cir. 

2017) (rejecting the patentee’s attempt to take a statement 

“verbatim” from the common specification where the statement “lacks the clear expression of intent necessary for a 

patentee to act as its own lexicographer”).

The majority treats the ’027 patent as persuasive, however, because the two patents purportedly share “common 

subject matter” and “[t]he patentees demonstrated in the 

’926 patent the same understanding of 100%” that is reflected in the ’027 patent. Majority Op. at 15. But the ’926 

patent is a continuation-in-part of the ’027 patent with a 

different specification. And the applicant chose to write 

this new specification without mentioning “carrier material” or incorporating the ’027 patent by reference, which 

underscores the impropriety of importing that limitation 

into the ’926 patent claims. See, e.g., Trading Techs. Int’l, 

Inc. v. Open E Cry, LLC, 728 F.3d 1309, 1323 (Fed. Cir. 

2013) (distinguishing between a patent and its continuation-in-part parent for purposes of claim construction 

where the former “include[d] extensive disclosures that 

were not present” in the latter). It also indicates that the 

subject matter of these patents is not common in the only 

way that matters for interpreting these claims. The majority, thus, relies on a commonality that does not exist.

Worse still, the ’027 patent does not contain a claim 

limitation analogous to “100% by weight.” This difference 

implies that the ’027 patent and the ’926 patent claims 

were intended to have different scopes. The district court’s 

and the majority’s heavy reliance on the ’027 patent is 

therefore unjustified. See Advanced Cardiovascular Sys., 

Inc. v. Medtronic, Inc., 265 F.3d 1294, 1305–06 (Fed. Cir. 

2001) (refusing to consider prosecution history of related 

patent where there were “no common claim terms in dispute” across the patents); ResQNet.com, Inc. v. Lansa, Inc., 

346 F.3d 1374, 1382 (Fed. Cir. 2003) (“These similarities 

reflect the parentage of the ’608 patent, which is a continuation-in-part (CIP) of the ’961 patent. Although the 
E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC 9

related patents are similar, their claims are not identical . . . This difference is significant. Therefore, this court 

interprets the claim anew, without regard to the interpretation of claim 1 of the ’961 patent.”).

Of course, a parent patent is relevant to claim construction issues involving its continuation-in-part child and 

therefore ought to be considered for its probative value. 

See, e.g., Jonsson v. Stanley Works, 903 F.2d 812, 818 (Fed. 

Cir. 1990) (acknowledging it was “not disputed” that the 

two patents contained similar limitations); Wang Labs., 

Inc. v. Am. Online, Inc., 197 F.3d 1377, 1383 (Fed. Cir. 

1999) (concluding that the patents had common subject 

matter); Ormco Corp. v. Align Tech., Inc., 498 F.3d 1307, 

1314 (Fed. Cir. 2007) (noting that the specifications of the 

parent and child patents “have the same content”). 

But that value is limited where the two patents recite different claims based on different specifications using different words. To be sure, Jonsson and its progeny emphasized 

the value of certain statements made during the prosecution history of a parent patent. See Jonsson, 903 F.2d at 

818 (discussing “arguments and remarks” offered during 

prosecution of the parent patent to distinguish it from the 

prior art); Wang, 197 F.3d at 1384 (considering arguments 

made “during the prosecution of the parent application” to 

distinguish the parent from a prior art reference); Ormco, 

498 F.3d at 1314 (“When the application of prosecution disclaimer involves statements from prosecution of a familial 

patent relating to the same subject matter as the claim language at issue in the patent being construed, those statements in the familial application are relevant in construing 

the claims at issue.”). But, as noted above, the majority 

imports a limitation from the parent patent’s specification

which was removed from the ’926 patent.4 At the very 

 

4 The parent patent’s specification is certainly part 

of the child’s prosecution history. But statements from the 
10 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

least, it is improper to rely so heavily on a related patent’s 

specification to drive the claim construction analysis of a 

different patent, as the district court and majority appear 

to have done here. 

III. THE DISTRICT COURT’S CONSTRUCTION OF 

“100% BY WEIGHT” LED THE JURY ASTRAY

The district court’s construction created confusion at 

trial and distracted the jury from its infringement inquiry 

because the construction shifted focus away from the concentration of platelets in the refractory layer. As a result, 

the jury was asked to determine whether certain non-platelet additives count as “carriers” or “dispersants,” even 

though neither term is mentioned in the claims. And those 

terms were moving targets throughout the trial. For example, the jury received competing definitions—as well as 

permutations of similar definitions—from the parties. 

See, e.g., J.A. 6080, 681:19–23 (DuPont’s expert testified

that “push[ing] materials apart or help[ing] them separate” 

is “one of the things [a dispersant] can do” (emphasis 

added)); J.A. 6081, 682:2–6 (DuPont’s expert testified that 

a “[c]arrier can mean many things” and that “it’s kind of a 

vague term”). 

This confusion led the jury to conclude, improperly,

that Unifrax’s 95%-platelet refractory layer satisfies the 

 

parent patent’s specification that fall short of lexicography 

do not have the same force as arguments about claim scope 

from the prosecution history. See Ormco, 498 F.3d at 1314 

(“While all those statements by the inventors in the specification of the Ormco patents, standing alone, may not be 

conclusive in showing that the claims require completely 

automatic determination of final tooth positions, those in 

the prosecution history make it even clearer.”).
E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC 11

claims’ 100%-platelet requirement.5 But that defies the 

plain claim language, as well as common sense, and should 

not be permitted to stand. See CytoLogix Corp. v. Ventana 

Med. Sys., Inc., 424 F.3d 1168, 1173 (Fed. Cir. 2005) (“[I]t 

appears that the conflicting expert views as to claim construction created confusion and may have led to a verdict 

of infringement with respect to the asserted claims of the

’061 patent that was not supported by substantial evidence . . . .”).

For these reasons, I would vacate the district court’s 

construction of “100% by weight” and adopt instead the 

term’s plain meaning—i.e., that the refractory layer must 

comprise a 100%-platelet composition when dry, and that, 

only after the remaining steps of the manufacturing process are completed may there be up to 10% of residual moisture remaining. Because DuPont does not dispute that 

 

5 The district court “acknowledge[d] the possibility 

that [its] construction of ‘100% by weight’ may yield questions in the future regarding the meaning of other terms,” 

E.I. du Pont, 2016 WL 158031, at *10, but the court declined to subsequently construe those other terms. To be 

clear, there is nothing inherently wrong in this decision. 

District court judges are often faced with the difficult task 

of avoiding the “O2 Micro trap” that inevitably arises when 

ambiguous claims terms are left unconstrued, while simultaneously managing their patent cases to ensure efficient 

and orderly resolution and to deter belated claim construction proposals. See Nobelbiz, Inc. v. Global Connect, L.L.C., 

876 F.3d 1326, 1328–29 (Fed. Cir. 2017) (O’Malley, J., dissenting from the denial of en banc rehearing). We should 

generally defer to district court judges on such matters. 

See id. Here, however, the district court’s construction created ambiguity where there should have been none. 

In such instances, district courts must be vigilant to resolve such ambiguities. 
12 E.I. DUPONT DE NEMOURS & CO. v. UNIFRAX I LLC

Unifrax’s product does not infringe under that construction, I would reverse the district court’s denial of JMOL as 

to noninfringement. See Finisar Corp. v. DirecTV Grp., 

Inc., 523 F.3d 1323, 1333 (Fed. Cir. 2008) (“If no reasonable 

jury could have found infringement under the proper claim

construction, this court may reverse a district court’s denial of JMOL without remand.”).