A court battle involving an attempt by C. Schmidt & Sons Inc., a Philadelphia brewer, from purchasing 29 percent interest in F&M Schaefer Corp., a New York beer maker, has heated up in recent days.

The major issue of controversy is a motion by Schaefer to have certain documents "dealing with the relationship of the plaintiffs (Schaefer) and their bank" sealed under a protective order. Schmidt's attorneys requested the records in discovery motions.

Meanwhile, in U.S. District Court Judge Vincent Broderick in New York has issued an order temporarly preventing Schmidt from buying the Schaefer stock.

Schaefer contends that the purchase would violate federal antitrust laws, since the two breweries together account for almost half of all beer sales in the New York City area.

Schmidt, which sells beer under the brand names Schmidts, Rheingold and Knickerbocker, has about 24.7 percent of the New York market, while Schaefer, which sells under the Schaefer and Piels labels, has about 23 percent.

In the Philadelphia market, the two firms account for about 35 percent of beer business.

U.S. Magistrate Harold J. Rabby, who heard arguments on motions in the case over the past two days, said the public release of the documents could "result in dire economic consequences to (Schaefer) without at the same time conferring any contravailing substantial benefit to (Schmidt)."

The controversy began on April 3 when, according to court papers, Schmidt's officials met with Citibank officials. The latter agreed to sell to Schmidt $20 million worth of notes that could be converted into 769-232 shares of common stock in Schaefer, or 29 percent of Schaefer's outstanding stock.

Schaefer then obtained the restraining order to prevent the sale. The order remains in effect through Monday, when both sides are to appear in court for trial.

Until that time, the court, in a five-page secrecy order, has ruled that access to all potentially disputed documents is restricted to the attorneys in the case, who were ordered not to discuss them.