Continuous Single-Side Coating for Oral Patches

Continuous Single-Side Coating for Oral Patches

For oral patches, local delivery patches and certain functional single-side films, the industry is steadily moving away from manual, intermittent operations and toward continuous, engineered lines. Once a project enters scale-up, questions about coating uniformity, drying stability and cleaning validation quickly become hard requirements, not “nice-to-have” items.

Single-side coating looks simple on paper – just spray, dry and wind. In reality, the way those three steps are engineered determines whether the process is truly industrializable.

Why Single-Side Coating Is Harder Than It Looks

From a distance, single-side coating for oral patches seems straightforward. In practice, three groups of issues tend to decide whether a line will behave well under GMP conditions:

  • Coating uniformity
    Variations in spray pattern, flow rate or coating distance can lead to local loading differences, especially for small, targeted patch areas or dose-dense products.
  • Drying and exhaust
    Unstable drying – inadequate exhaust, uneven temperature or poor air distribution – can cause sticking, residual solvent problems and surface defects.
  • Stability of continuous conveying
    The choice of carrier web, support surface, tension control and positioning determines whether patches can be coated, dried and cut with repeatable alignment and yield.

When these three elements are treated as isolated “components”, scale-up often runs into hidden bottlenecks: batch-to-batch variation, difficult cleaning validation, or a process that only works when one particular operator is standing next to the line.

What CN2586476Y Brings: A Structured Path for Industrialization

Chinese utility model CN2586476Y focuses exactly on this question: how to turn single-side coating for patches into a continuous, industrializable structure, instead of a loose collection of hardware.

The patent’s key value is in how it organises: feed → spray → exhaust-assisted drying → continuous conveying into a coherent path that emphasises continuity, uniformity and maintainability. In essence, it:

  • stabilises the way fluid is supplied and sprayed onto the moving substrate,
  • ensures that drying is supported by controlled hot air and exhaust rather than passive heating,
  • and couples all of this with a conveying concept designed for repeatable tension and positioning.

This is the kind of structure that makes single-side coating truly upgradeable from lab-scale experiments to GMP-ready production.

HUANGHAI’s Approach: Single-Side Coating as an Engineered Package

Drawing on its experience in ODF and patch coating systems, HUANGHAI treats single-side coating as a process package, not just a “spray head plus tunnel”. The engineering focus is on three linked control points:

  • coating uniformity,
  • controllable drying with exhaust,
  • and stable continuous conveying.

By delivering these as an integrated solution, HUANGHAI helps customers build processes that are easier to scale, validate and operate consistently.

1. Coating Uniformity: Beyond “Does It Spray?”

For oral and local patches, dose accuracy depends heavily on local coating weight. HUANGHAI’s designs focus on:

  • consistent supply conditions (pressure, flow and filtration),
  • controlled nozzle distance and angle relative to the web,
  • and synchronisation between spray pattern and web speed.

The goal is to keep coating weight variation within tight limits across the entire coating width and along the machine direction, even as projects move from pilot trials to routine manufacturing.

2. Drying with Exhaust: Stable Films, Fewer Defects

Drying is not just a heater. For single-side patches, poor drying control can lead to:

  • sticking or blocking between layers,
  • surface defects such as orange peel or pinholes,
  • residual solvent values that drift near (or beyond) specification limits.

HUANGHAI applies controlled hot-air and exhaust concepts – including gradient or zone-based profiles where appropriate – so that solvent removal is effective and uniform. This aligns with its broader work on gradient hot-air drying for ODFs and patches across the Pharmaceutical Film Manufacturing Solutions portfolio.

3. Continuous Conveying: The Backbone of Repeatability

Finally, even the best spray and drying settings cannot compensate for unstable conveying. HUANGHAI’s single-side coating concepts emphasise:

  • appropriate carrier web or support surfaces for the specific patch format,
  • tension control matched to film thickness and adhesive layer behaviour,
  • and positional stability to support clean cutting and packaging downstream.

This combination makes it easier to keep yield and repeatability high, not just in a demo run but across real production campaigns.

What Customers Gain from a Structured Single-Side Coating Route

1. More Stable Loading

With coherent control over spray, drying and conveying, single-side coating can achieve:

  • more stable average coating weight,
  • reduced risk of local over- or under-dosing,
  • and less batch-to-batch variation in critical quality attributes.

This is particularly important for high-potency or narrow-therapeutic-window actives used in oral or local patches.

2. Fewer Defects and Lower Rework

A balanced drying and conveying design leads to fewer issues such as:

  • sticking or blocking when rewinding or stacking,
  • surface marks or voids that complicate inspection,
  • residual solvent excursions that trigger additional testing or rework.

In turn, this improves first-pass yield and reduces the hidden cost of troubleshooting.

3. Easier Cleaning, Changeover and Validation

When the process route is structurally simple and control points are clearly defined, it also becomes:

  • easier to design cleaning procedures and visual inspection points,
  • more straightforward to document critical parameters for validation,
  • and quicker to perform changeovers between products and strengths.

This is where a patent-backed, engineered path such as CN2586476Y adds real value: it provides a logic that your quality and engineering teams can explain and defend during audits.

Related HUANGHAI Equipment and Solutions

HUANGHAI implements single-side and multi-purpose coating concepts across its ODF and patch platforms, allowing customers to cover both R&D and commercial needs with the same engineering logic.

MJ150-L – Pilot and Medium-Scale Coating & Drying

The MJ150-L ODF Film Coating Machine supports both ODF and patch-type coating and drying, and is well suited to:

  • developing and optimising single-side coating recipes,
  • testing different spray and drying settings for oral or local patches,
  • and generating data packages for registration and scale-up planning.

MJ150 – Commercial-Scale Production

For commercial output, the MJ150 ODF & Transdermal Patch Film Making Machine extends the same design principles to higher throughput, enabling:

  • continuous single-side coating and drying for oral and transdermal patches,
  • stable tension and web handling across long production runs,
  • and smooth integration with slitting, die-cutting and packaging modules.

For a wider context on how these lines fit into an end-to-end strategy, see:

Conclusion: Industrial Single-Side Coating Is Defined by Control, Not Just Hardware

The industrialisation of single-side coating does not depend on whether you have a spray nozzle. It depends on whether the system can ensure:

  • uniform coating across and along the web,
  • stable drying and exhaust that protect quality and residual solvent,
  • and continuous conveying that is repeatable and easy to validate.

By following the structured route described in CN2586476Y and applying ODF/patch coating experience on MJ150-L and MJ150 lines, HUANGHAI delivers more than a piece of equipment – it delivers an engineered process path that makes scale-up and validation easier.

If you are planning an oral patch, local delivery patch or single-side functional film project and want to move from intermittent operations to a robust continuous route, our team can help map the right coating–drying–conveying configuration for your needs.

Contact HUANGHAI to discuss continuous single-side coating solutions for your next patch or film line.

Back to blog

Contact us