Kolon Industries Inc v. HS Hyosung Advanced Materials Corp

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Kolon Industries, Inc. (Republic of Korea)
  • Defendant: Hyosung Advanced Materials Corp. (Republic of Korea) and Hyosung USA, Inc. (Delaware)
  • Plaintiff’s Counsel: Latham & Watkins LLP
• Case Identification: Kolon Industries, Inc. v. Hyosung Advanced Materials Corp., 8:24-cv-00415, C.D. Cal., 06/03/2024
• Venue Allegations: Venue is alleged based on Defendant Hyosung USA, Inc. maintaining a regular and established place of business in Irvine, California, within the district, and having committed alleged acts of patent infringement in the district.
• Core Dispute: Plaintiff alleges that Defendant’s hybrid tire cord products, composed of aramid and nylon fibers, and the methods used to make them, infringe three U.S. patents covering such technology.
• Technical Context: The technology at issue is high-performance hybrid tire cord (HTC), a critical reinforcement material for tires, with increasing importance for heavier, high-torque electric vehicles.
• Key Procedural History: The complaint alleges Defendants had pre-suit knowledge of the patents-in-suit via a February 2021 notice letter. It further alleges knowledge of the '663 patent from its citation during the prosecution of Defendants' own patent applications, and knowledge of the '731 patent from an unsuccessful attempt by Defendants to invalidate its Korean counterpart before the Korean Patent Trial and Appeal Board.

Case Timeline

Date	Event
2012-12-27	'731 Patent Priority Date
2015-06-29	'663 and '765 Patents Priority Date
2017-04-11	U.S. Patent No. 9,617,663 Issues
2017-10-17	U.S. Patent No. 9,789,731 Issues
2018-03-06	Hyosung receives ISR in a related PCT application citing the '663 Patent
2019-02-05	U.S. Patent No. 10,196,765 Issues
2019-05-30	Hyosung discloses '663 Patent during prosecution of its own patent application
2021-02-04	Kolon sends letter to Hyosung identifying the patents-in-suit
2021-03-10	Hyosung acknowledges receipt of Kolon's letter
2024-02-28	Original complaint filed in this action
2024-03-21	Korean Patent Trial and Appeal Board rejects Hyosung's invalidity challenge to the Korean counterpart of the '731 Patent
2024-06-03	Amended Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,617,663 - Hybrid Tire Cord and Method for Manufacturing the Same (Issued Apr. 11, 2017)

The Invention Explained

• Problem Addressed: The patent describes drawbacks in conventional methods of making hybrid aramid-nylon tire cords, which often involve complex, three-step processes using separate machines. These methods can result in unstable "covering structures" where one yarn wraps around the other, leading to low production efficiency, high manufacturing costs, and high defect rates (U.S. Patent No. 9,617,663, col. 2:15-32).
• The Patented Solution: The invention is a method for manufacturing hybrid tire cord that simplifies the process by performing all twisting steps—both the primary twisting of the individual aramid and nylon yarns and the secondary twisting of those yarns together—simultaneously and continuously in a single machine ("one twister"). A key feature is applying higher tension to the nylon yarn than the aramid yarn, which results in the aramid yarn being slightly longer than the nylon yarn if the final cord is untwisted. This creates a more stable structure and improves the cord's final properties ('663 Patent, Abstract; col. 3:5-32).
• Technical Importance: This single-machine process was designed to improve manufacturing efficiency and reduce costs, while the resulting stable cord structure enhances fatigue resistance and uniformity, properties critical for high-performance tires ('663 Patent, col. 3:35-51).

Key Claims at a Glance

• The complaint asserts independent claim 1 ('663 Patent, col. 8:36-57; Compl. ¶98).
• Claim 1 Elements:
  • A method of manufacturing a hybrid tire cord comprising a first step of primarily twisting an aramid filament yarn and a second, simultaneous step of primarily twisting a nylon filament yarn.
  • A third step, continuous with the first two, of secondarily twisting the two primarily twisted yarns together to form a plied yarn.
  • Performing all three steps using "one twister."
  • The primary twists of the nylon and aramid yarns are in the same direction, and the secondary twist is in the opposite direction.
  • Applying higher tension to the nylon filament yarn than the aramid filament yarn.
  • The differential tension results in the aramid yarn being 1.005 to 1.025 times longer than the nylon yarn if the secondary twist were untwisted.
• The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 9,789,731 - Hybrid Fiber Cord and Method for Manufacturing the Same (Issued Oct. 17, 2017)

The Invention Explained

• Problem Addressed: Like the '663 patent, this patent addresses the problems of conventional hybrid tire cord manufacturing, including low productivity, high defect rates, and unstable structures caused by using different twist numbers for the aramid and nylon components ('731 Patent, col. 2:1-41).
• The Patented Solution: The patent discloses a manufacturing method and the resulting product-by-process. The core innovation is a method where the nylon and aramid filaments are twisted with identical twist numbers (within a specific range of 300-500 TPM) and then secondarily twisted together to form a ply yarn where the two components have "identical structures." This process, which can be performed on a single machine like a "Cable Corder," results in a product with specific, desirable performance characteristics, such as high strength retention after fatigue testing and controlled shrinkage ('731 Patent, Abstract; col. 4:30-47).
• Technical Importance: By ensuring the twist numbers and resulting structures are identical, the method simplifies manufacturing and produces a highly stable and uniform cord where the two distinct materials function as a cohesive unit.

Key Claims at a Glance

• The complaint asserts independent claim 4 ('731 Patent, col. 11:1-24; Compl. ¶117).
• Claim 4 Elements:
  • A method comprising a first step of primarily-twisting a nylon filament at 300-500 TPM and a second step of primarily-twisting an aramid filament at 300-500 TPM.
  • A third step of secondarily-twisting the yarns together to produce a ply yarn where the nylon and aramid yarns have "identical structures with each other."
  • A step of coating the ply yarn with an adhesive.
  • The resulting coated yarn has a strength retention rate of 80% or more after a specific fatigue test and a dry heat shrinkage of 1.5% to 2.5%.
  • The first, second, and third twist numbers are all "identical with each other."
  • The third step produces a 2-ply yarn consisting of one ply of nylon and one ply of aramid.
• The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 10,196,765 - "Hybrid Tire Cord and Method for Manufacturing the Same" (Issued February 5, 2019)

• Technology Synopsis: This patent claims the physical hybrid tire cord product itself, rather than the method of making it. It addresses the instability of conventional "covering structures" by claiming a cord with a "merge structure" where the aramid and nylon yarns are twisted together. The key limitation is that if the final cord is untwisted, the aramid yarn component is between 1.005 and 1.025 times the length of the nylon yarn component, a feature intended to improve fatigue resistance by dispersing stress between the two materials (U.S. Patent No. 10,196,765, Abstract; col. 4:2-18).
• Asserted Claims: Independent claim 1 is asserted (Compl. ¶134).
• Accused Features: The complaint alleges that Hyosung's two-ply HTC product infringes by comprising a nylon and an aramid primarily twisted yarn that are secondarily twisted together, where the aramid yarn is allegedly 1.014 times the length of the nylon yarn upon untwisting and has a "merge structure having a partial covering structure" (Compl. ¶¶135, 138, 140).

III. The Accused Instrumentality

Product Identification

The accused product is "Hyosung's two-ply HTC composed of one ply of aramid and one ply of nylon" (Compl. ¶97). This product is marketed as "Aramid & Hybrid Tirecord," with the aramid component sold under the tradename ALKEX® (Compl. ¶¶45, 63).

Functionality and Market Context

The accused HTC serves as a reinforcement material in high-performance tires, particularly for the growing electric vehicle (EV) market, which demands stronger tires due to increased vehicle weight and instant torque (Compl. ¶1). The complaint alleges Hyosung uses a "direct cabler" to manufacture the HTC, a machine that performs primary and secondary twisting in a single, simultaneous process (Compl. ¶¶102, 104). The HTC is allegedly sold to tire manufacturers like Hankook, which incorporates it into tires for vehicles such as the 2024 Kia EV9 and 2024 Hyundai Ioniq 6 that are sold in the U.S. (Compl. ¶¶56-57, 61). A microscopic image shows the accused HTC is a plied yarn of two different materials, one appearing as a twisted bundle of yellow-orange fibers (aramid) and the other as white fibers (nylon) (Compl. ¶103).

IV. Analysis of Infringement Allegations

'663 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
a first step of primarily twisting an aramid filament yarn in a first direction to form an aramid primarily twisted yarn;	Hyosung's manufacturing method includes a step of primarily twisting aramid filament yarn. A microscopic image shows a primarily twisted aramid filament yarn.	¶100	col. 3:11-13
a second step of primarily twisting a nylon filament yarn in a second direction... the second step and the first step being conducted simultaneously;	Hyosung's method includes a step of primarily twisting nylon filament yarn, which is conducted "at the same time" as the aramid twisting. A microscopic image shows a primarily twisted nylon filament yarn.	¶¶101-102	col. 3:14-16
a third step of secondarily twisting the aramid primarily twisted yarn and the nylon primarily twisted yarn... to form a plied yarn, the third step being conducted continuously with the first and second steps,	Hyosung's method includes a third step of secondarily twisting the aramid and nylon yarns together to form a plied yarn, which is conducted continuously with the primary twisting steps.	¶¶103-104	col. 3:17-20
wherein the first, second and third steps are conducted by one twister,	Hyosung allegedly uses a single "direct cabler," which is a type of twister that performs all steps simultaneously.	¶¶102, 105	col. 3:20-21
tension applied to the nylon filament yarn in the second step is higher than tension applied to the aramid filament yarn in the first step in such an amount that... the aramid primarily twisted yarn would be 1.005 to 1.025 times longer than the nylon primarily twisted yarn.	Hyosung allegedly applies differential tension such that a measured sample of its product shows the aramid yarn is about 1.014 times longer than the nylon yarn upon untwisting. This allegation is also supported by statements in Hyosung's own published patent application.	¶¶107-108	col. 3:23-32

• Identified Points of Contention:
  • Scope Questions: A central question is whether Hyosung's actual, commercial manufacturing process can be proven to match the specific method claimed. The complaint relies heavily on inferences from Hyosung's own patent application ('414 published application) to allege the use of a "one twister" and simultaneous twisting (Compl. ¶¶102, 104). The case may turn on whether discovery confirms this process is used for the accused products sold in the U.S.
  • Technical Questions: What evidence will confirm that the tension applied by Hyosung's process consistently results in the specific length ratio (1.005-1.025) required by the claim? The complaint provides a single measurement of "about 1.014" for one sample, raising the question of whether this is representative of all accused products (Compl. ¶107).

'731 Patent Infringement Allegations

Claim Element (from Independent Claim 4)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
a first step for primarily-twisting a nylon filament at a first twist number of 300 to 500 TPM...	A sample of Hyosung's product allegedly has a nylon yarn with a twist number "at or slightly above 300 TPM."	¶118	col. 6:29-31
a second step for primarily-twisting an aramid filament at a second twist number of 300 to 500 TPM...	A sample of Hyosung's product allegedly has an aramid yarn with a second twist number "at or slightly above 300 TPM."	¶120	col. 6:29-31
a third step for secondarily-twisting the... yarns together... such a way that the nylon and aramid primarily-twisted yarns have identical structures with each other... wherein the first, second and third twist numbers are identical with each other...	Hyosung allegedly uses a "direct cabler" to twist the yarns at a "single twist number," which results in the yarns having identical twist numbers and "identical structures with each other." A microscopic image shows the resulting plied yarn.	¶¶121, 124, 103	col. 4:3-4
coating the ply yarn with an adhesive, and the ply yarn coated with the adhesive has a strength retention rate of 80% or more... and has a dry heat shrinkage of 1.5 to 2.5%...	Hyosung's method allegedly includes coating the yarn with adhesive. The complaint alleges, on information and belief, that the final product meets the claimed strength and shrinkage properties to satisfy specifications from tire manufacturing partners like Hankook.	¶¶122-123	col. 5:40-44

• Identified Points of Contention:
  • Scope Questions: What is the precise meaning of "identical structures"? Does it require perfect geometric identity as shown in the patent's Figure 2, or can it be met functionally? This term appears central to distinguishing the invention from prior art where one yarn covers another.
  • Technical Questions: Can Plaintiff prove that the accused product, as a result of its manufacturing method, meets the specific performance metrics required by the claim (strength retention >80% and shrinkage of 1.5-2.5%)? The complaint alleges this on "information and belief" based on customer specifications, suggesting a future battle over product testing and evidence (Compl. ¶123).

V. Key Claim Terms for Construction

For the '663 Patent

• The Term: "conducted by one twister"
• Context and Importance: This limitation is fundamental to the patent's claimed advance over prior art multi-step processes that used multiple, separate twisters. Proving that Hyosung uses a single, integrated machine for all three twisting steps is essential to the infringement allegation. Practitioners may focus on this term because it defines the core of the asserted manufacturing method.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claim language itself is "one twister," which could be argued to encompass any single piece of machinery capable of performing the claimed steps, regardless of its specific commercial name or internal mechanics.
  • Evidence for a Narrower Interpretation: The '765 patent, of which the '663 patent is a continuation, explicitly mentions a "cable cord twister" in its detailed description as an example of a machine that can perform the process (U.S. Patent No. 10,196,765, col. 5:60-61). A defendant may argue that the prosecution history limits the term "one twister" to this specific type of machine.

For the '731 Patent

• The Term: "identical structures"
• Context and Importance: This term is the lynchpin of the claim's novelty, distinguishing the invention from prior art "covering" structures. The infringement analysis for the '731 patent will depend heavily on whether the accused product's physical arrangement of nylon and aramid yarns qualifies as having "identical structures."
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The patent's abstract explains the goal is for the yarns to be "secondarily-twisted together to have identical structures with each other," which could be interpreted functionally to mean they are integrated in a way that they behave identically under stress, without requiring perfect geometric symmetry.
  • Evidence for a Narrower Interpretation: The patent explicitly includes FIG. 2 to illustrate the invention, which shows a distinct, side-by-side arrangement of the two yarns (110 and 120). This is contrasted with FIG. 1, labeled "PRIOR ART," which shows a "covering" structure where one yarn (12) wraps around the other (11) ('731 Patent, col. 2:25-33; FIG. 1-2). A defendant will likely argue that "identical structures" must be interpreted in light of FIG. 2 to mean a non-covering, parallel configuration.

VI. Other Allegations

• Indirect Infringement: The complaint alleges both inducement and contributory infringement for all three patents. Inducement is based on allegations that Hyosung knowingly provides the accused HTC to tire manufacturers (e.g., Hankook) and provides technical support, intending for them to incorporate the HTC into tires that are imported and sold in the U.S., thereby infringing the patents (Compl. ¶¶110-111, 127-128, 142-143). Contributory infringement is based on allegations that Hyosung sells or imports aramid filament yarn knowing it is specially made for use in the infringing HTC and is not a staple article of commerce (Compl. ¶¶112, 129, 144).
• Willful Infringement: The complaint makes extensive allegations of willful infringement. It claims Hyosung had pre-suit knowledge of the patents from at least a February 4, 2021 letter from Kolon (Compl. ¶30). It further alleges Hyosung was aware of the '663 patent as early as March 2018 from the prosecution of its own patent applications, where the '663 patent was cited as prior art (Compl. ¶¶33-35). Finally, it alleges Hyosung's failed attempt to invalidate the Korean counterpart to the '731 patent demonstrates knowledge and a deliberate decision to continue infringing (Compl. ¶32).

VII. Analyst’s Conclusion: Key Questions for the Case

• A key evidentiary issue will be one of process verification: Can Kolon prove, through discovery, that Hyosung's commercial manufacturing for its HTC products sold in the U.S. actually uses the "one twister" method with the specific tensioning and twisting parameters required by the '663 and '731 method claims, or will there be a material difference between the accused process and the claims?
• A central legal issue will be one of claim construction: How will the court construe the term "identical structures" from the '731 patent? The outcome may depend on whether the term is interpreted to require the strict, side-by-side geometric arrangement depicted in the patent's figures or if a more functional definition is adopted, and whether the accused product meets that standard.
• Given the extensive allegations of pre-suit notice through direct correspondence, patent prosecution history, and foreign litigation, a critical question will be one of culpability: If infringement is found, will the evidence support a finding of willful infringement, exposing Hyosung to the possibility of enhanced damages and an exceptional case finding for attorney's fees?