VWR International, the slow-growing, Radnor-based lab chemicals, glass, and instruments maker, has agreed to sell out to Avantor Performance Materials, a Lehigh Valley-based company whose owner, Wall Street buyout giant New Mountain Capital, uses it to acquire rivals, cut costs, and squeeze more profits in the global lab-supply business.

Shares of VWR fell after CEO Manuel Brocke-Benz confirmed the sale and canceled Friday morning's first-quarter conference call with investors.

Brocke-Benz's board sold for $33.25 a share, or $4.3 billion — disappointing investors excited by Wall Street Journal reports that predicted the sale, but exaggerated the price.

Traders bid VWR stock up from around $28 earlier this week, to a record $34 at Thursday's closing, before falling back to a little below the purchase price.

In his statement announcing the sale, CEO Brocke-Benz said the deal valued his company at $6.4 billion — the "enterprise price" including VWR plus the stock.

VWR employs 10,000 at its U.S. and foreign facilities. The company moved its offices and 375 workers to Radnor from Chester County in 2010.

The buyer didn't announce whether it will fire headquarter's staff at VWR's Radnor offices, or at Avantor's Bethlehem-area headquarters, or say which plants it might consolidate and close. A spokesman for New Mountain was not immediately available.

VWR's largest owner, which will benefit from the sale, is investment bank Madison Dearborn Partners, which owns about 35 percent. Vanguard Group and other big mutual fund companies are also shareholders.

Madison Dearborn was also a leading VWR owner before the company went public, selling shares to investors in 2014. The stock closed at $21.05 on its first day of trading.

Since then, VWR sales have grown in the low single digits each year, to around $4.5 billion a year, including acquisitions. First-quarter sales totaled $1.14 billion, the company said in a statement Friday. Earnings totaled $38.5 million, down slightly from $38.8 million a year earlier.

Avantor, VWR's new owner, has closed plants and laid off workers, as the Allentown Morning Call has reported, at its own operations since New Mountain Capital bought the company — formerly known as Mallinckrodt Baker and based in Phillipsburg, N.J. — for $280 million in the recession year 2010.

New Mountain was founded by veteran Goldman Sachs buyout artist Stephen Klinsky in 1999, and says it has invested more than $8.5 billion in corporate buyouts since then.

Mallinckrodt Baker had been part of Covidien Corp., which was split off from the former Princeton-based conglomerate Tyco International by CEO Edward Breen as a way to boost investor profits in the face of disappointing share prices for the conglomerate.

Breen, of New Hope, has made similar plans to break up the DuPont Co., which he now runs, and its merger partner, Dow Chemical Co. Breen also serves as an advisor to New Mountain.