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Seeking Solutions To Manage CO2 Formation In Thick Polyurethane Coating Films

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Type of Solution sought

  • A Material
  • A Technology
  • An application method

Description of Desired Solution

A SpecialChem Client is seeking new chemistry, additives, or novel application techniques to avoid the formation of CO2 bubbles when applying moisture-cured polyurethane (PUR) coating at a thickness of 200µm or higher .

Background

When forming a moisture-cured PUR coating, the reaction of isocyanate with water forms carbon dioxide. When it stays in the film the gas forms bubbles. These bubbles affect the physical-mechanical properties of the film and inhibit the coating’s resistance to corrosion.

To contain the loss in corrosion resistance, the maximum film thickness is currently restricted to ~100 microns - dry film thickness.

This is a limitation in many applications, and particularly for applied coatings on complex objects; such as I-beams and bridges, where precise control of film thickness is particularly challenging.

The SpecialChem Client is ready to consider chemical, filler, and application process changes. If a filler solution is proposed, modifications will also be required to the coating application process which currently uses all liquid reactants.

Detailed Solution Description

These coatings are typically either brush / rolled or spray-applied in the field, and are preferentially used as a maintenance coating due to their single component being easy to use.

Currently, prepolymers are used to lower the isocyanate concentration in moisture-cured PUR coatings, reducing the formation of carbon dioxide.

The Client is willing to work with the solver to fine-tune the approach and make samples. The Client can also perform any required material characterization, analytical work, and physical testing required to validate the solution.

The SpecialChem Clients seeks solutions that would allow:

  • Homogeneous coating: bubble free
  • Moisture cured at 50 – 80% Relative Humidity
  • Thickness of dry film should be ~200 microns or more
  • Curing times below 8 hours

Possible Routes To Investigate

  • Chemical solutions may include modification of the coating formulation with novel surfactants, chelating agents, scavengers, etc.
  • Solutions may also suggest modifications to the isocyanate and/or soft segment intermediates used to make the coating.

Solution that are not of interest

Efforts to reduce bubbles/defects by reducing cure speed have proven to be effective by lowering the concentration of tin catalyst, and the longer “open time” allows the bubbles to escape before a hard film is formed; however the slower cure speed leads to unacceptably long curing times (up to 24 hr).

Anticipated Next Steps with Respondents

As soon as realistically possible.

Type of Outcome expected

  • Ready to use solutions
  • Will partner to develop a commercial solution

Company Demographics

  • Industry: Chemical Industry
  • Annual Revenue: > 10 Billion Euro
  • Years in Business: > 50 years
  • Headquarters Area: Germany

Business considered

  • Buying
  • Licensing
  • Contractual partnership (R&D, marketing…)