The Civil Aeronautices Board yesterday denied a request by Continental Airlines for a 10-day delay in the board's earlier decision allowing Texas International Airlines to buy up to 48 1/2 percent of Continental's stock -- stock it plans to use to vote against Continental's proposed merger with Western Airlines.

The board's action came in response to a petition from Continental asking for a stay so that its employe groups would have time to make a counter tender offer for the Continental stock. Texas International can begin buying shares tendered to it today.

The board said it had no statutory basis to interfere with the TI tender offer.

Before the CAB issued its order, Cab Chairman Marvin S. Cohen returned to his office to find 32 helium-filled balloons tied to the arm of his chair, according to a CAB spokesman. A note was attached which read, "Don't burst our bubble. Please let Continental employes run their own airline." The communication is considered a violation of the board's rules and was sent to the docket room to be filed in the public record, the spokesman said.

The board's action followed a similar denial by the U.S. Court of Appeals that the board's approval of the stock purchase plan be stayed. In a related development, a federal court in Los Angeles turned down a Continental request for a stay based on alleged securities law violations.