Self-Cleaning Coating… or not?

Title: SELF-RENEWING HYDROPHILIC ORGANIC COATINGS

 Number/Link: US2014/018466

Applicant/Assignee: Empire Technology

Publication date: 16-01-2014

Gist”: Coating containing free amine groups resulting in a hydrophilic surface that is supposedly self-cleaning.

Why it is interesting: Conventionally “self-cleaning” surfaces are produced using hydrophobic coating compositions resulting in surfaces with low contact angles with respect to water.  The current case claims that highly hydrophilic surfaces also show a self-cleaning effect.  An emulsion-polymerized polymer with blocked-isocyanate side groups is used as a coating composition.  After the coating is applied the side groups are deblocked by atmospheric moisture resulting in (hydrophilic) amine groups.  In an example 2-methyl-acrylic acid 2-isocyanatoethyl ester blocked with 3,5-dimethylpyrazole was emulsion polymerized and, together with additives, used as a coating composition.
While this is fun chemistry I very much doubt that this coating would be truly self-cleaning.  The amine groups will surely react with all kinds of stuff in the air possibly resulting in quite the opposite.

deblocking of the isocyanate side groups under the influence of water.

deblocking of the isocyanate side groups under the influence of water.

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