Who invented hair spray?

The first U.S patent describing copolymers for hair styling (called "Dressing of hair") dates back to 1942.

http://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=2305356&KC=&FT=E&locale=en_EP

According to WIkipedia, "Hair spray (also hair lacquer, spritz, or sticky water) is a common household aqueous solution that is used to keep hair stiff or in a certain style. Weaker than hair gel, hair wax, or glue, it is sprayed to hold styles for a long period. Using a pump or aerosol spray nozzle, it sprays evenly over the hair. May leave hair feeling "crunchy" unless brushed out. Hair spray was first developed and manufactured in 1948 by Chase Products Company, based in Broadview, Illinois."

https://en.wikipedia.org/wiki/Hairstyling_product#Hair_spray

As is often the case, particularly when a product such as hair spray is poorly defined in differentiating it from other similar products, it is difficult to pinpoint a single inventor.