Finishing its exit from the former Rohm & Haas Co. headquarters on Independence Mall, Dow Chemical told about 350 employees there Wednesday that they would be relocated to a suburban corporate center in Collegeville by mid-2016.

The move is part of a several-step realignment of Dow facilities in the Philadelphia region that combines researchers at the former Rohm & Haas Spring House facility in Montgomery County and the business staff in Center City in leased space at the underused Pfizer pharmaceuticals complex.

"The intention of this is to get that center of gravity into one building," Dow spokeswoman Christine Miller said.

Center City employees were told of the planned relocation in e-mails and staff meetings, and they will be part of the planning related to it over the next year, Miller said.

The move may be a hardship for many who take SEPTA mass transit to the Independence Mall offices. A number of employees commute from Bucks County because of the company's big chemical complex in Bristol Borough, which has been a feeder for employees to downtown offices.

The landmark Rohm & Haas headquarters on Independence Mall opened in 1964 as part of a redevelopment of the area. In addition to other design flourishes, the building came with Plexiglas chandeliers in the burnished-wood lobby. Rohm & Haas developed and commercialized the once-innovative plastic.

Today, the specialty-chemical company's headquarters is an anomaly on Independence Mall, a tourist area. Offices there belong mostly to federal agencies and nonprofit organizations, while Philadelphia companies seem to locate their offices west of Broad Street or at the Navy Yard.

These days, the Rohm & Haas building - or at least its elevated plaza - has been transformed into a millennials hangout, with the Independence Beer Garden drawing 1,000 or more patrons a day to its three bars, picnic tables, and parlor games. A beer garden manager said Wednesday afternoon that Dow's decision "has nothing to do with us" as he chatted with security guards.

La Colombe also recently opened a shop on the ground floor of the building.

Midland, Mich.-based Dow, with 52,000 employees, overpaid for Rohm & Haas in the midst of the financial crisis in 2009 and has rigorously cut costs since then as it folded the Philadelphia operations into its corporate structure.

Initially, Dow expressed support for local executive managers to run Rohm & Haas and a desire to stay in the city. But those plans seemed to fade. Dow's Philadelphia-area operations are focused, in part, on paints and chemicals used in the electronics industries.

The remaining Dow employees downtown are situated on 41/2 floors of the nine-floor building. Dow's facility in Collegeville is expected to employ 1,100 to 1,200 after the Center City employees are relocated there. Dow said in 2013 that it had a 50-year lease on the suburban facility.