Patsy Sherman of Bloomington, a retired 3M chemist who co-invented Scotchgard when she was in her 20s, died Monday in Minneapolis.

Sherman, who suffered a stroke in December, was 77.

In 1953, Sherman and Samuel Smith focused on an accident in a 3M lab, after an experimental compound dripped on someone's canvas tennis shoes and couldn't be cleaned off.

Sherman and Smith started thinking about an idea that seemed impossible at the time, a fluorochemical polymer that could repel oil and water from fabrics, according to a Jan. 8, 2005, Star Tribune article.

In 1956, their joint research resulted in the first sales of a Scotchgard product, a stain repellent for wool.

Sherman continued to develop a line of Scotchgard products, and in 2001 she was inducted into the National Inventors Hall of Fame. She held more than a dozen patents.

Smith died in 2005.

Investigations on the effect of perfluorochemicals (PFCs), formerly used in Scotchgard and other products, on the environment and human health continue. It has turned up in water, animals and people around the world, and it doesn't break down easily.

In some studies, the chemicals have been shown to cause cancer and liver and thyroid problems in animals, but no adverse health effects have been found in humans.

3M still sells Scotchgard using a different formula.

Sherman graduated in 1948 from Minneapolis North High School. In the early 1950s, she earned bachelor's degrees in chemistry and mathematics at Gustavus Adolphus College in St. Peter, Minn.

In 1952, she began work as a chemist at 3M, later becoming a laboratory manager. In the mid-1980s, she developed and ran the company's technical education department.

"She was a very great scientist," said Tony Manzara of Lake Elmo, who went to work for Sherman in 1977. "She was very open-minded and innovative, and she was a quick-thinking person."

Manzara said she was a witty friend to many.

As a member of professional groups, Sherman spoke before school groups and others, encouraging young people to go into science as a career.

She said in a 1994 Star Tribune article that her father set an example with his own scientific curiosity and encouraged and challenged her.

"Girls should follow their dreams. They can do anything anybody else can do," she said. "They have many more role models today -- not the least of whom might be their mothers."

Sherman's daughter, Sharilyn Loushin, of Eagan, is a 3M chemist, and another daughter, Wendy Heil of Waukesha, Wis., is a biologist who owns a precision optics company.

"She passed along her love of science to younger girls," Heil said. "She wanted other people to experience the joys she found in it."

Sherman's husband, Hubert, died in 1996.

In addition to her daughters, she is survived by her sister, Mary (Betty) Stevens of Ottumwa, Iowa, and two granddaughters.

Services will be held at 11 a.m. on Friday at Atonement Lutheran Church, 601 E. 98th St., Bloomington. Visitation will be held at 10:30 a.m. Friday at the church.