NEW YORK - GAF Corp. says it has acquired more than 5 percent of the stock of troubled Union Carbide Corp.

The disclosure Tuesday appeared to fuel speculation on Wall Street that GAF might mount a bid to acquire all or part of Union Carbide.

Union Carbide's stock jumped $3 .50 a share to $52.37 1/2 in New York Stock Exchange composite trading after losing $1.87 1/2 on Monday following the release of toxic gas at its plant in Institute, W.Va. GAF's common stock rose $2 a share to $31.62 1/2.

GAF said it would detail its investment in Union Carbide later in a filing with the Securities and Exchange Commission that is required whenever an investor purchases 5 percent or more of a company's stock.

GAF spokesman Donald Heymann declined to comment further, saying he could not disclose exactly how many Union Carbide shares GAF had bought, or for what purpose they were acquired.

The Bass Brothers Enterprises Inc. of Fort Worth announced earlier this year that it had acquired 5.4 percent of Union Carbide's common stock.

Union Carbide currently has about 70.4 million common shares outstanding, giving it a market valuation of $3 .67 billion. With 5 percent of the stock, GAF would own at least 3 .5 million shares.

Tom Failla, a spokesman at Union Carbide's headquarters in Danbury, Conn., said he had no comment on GAF's announcement.

GAF is a Wayne, N.J.-based maker of chemicals and building materials. It earned $56.7 million on sales of $731.3 million last year.

The company is headed by Samuel J. Heyman, a Connecticut real estate developer who took control of GAF in December 1983 after waging a successful proxy fight while owning only 4.9 percent of GAF's stock.

Union Carbide is one of the nation's largest chemical concerns and recorded $9.5 billion in 1984 revenue.

But the company has had major problems recently. Last year a toxic gas leaked from a Union Carbide plant in Bhopal , India, killing 2,000 people. And on Sunday the gas leak at its Institute plant injured 135 people.

Union Carbide announced Tuesday it was temporarily suspending production and use of aldicarb oxime, the poison gas involved in the Institute leak, until officials determined how the accident occurred.

But company officials also said residents were exposed only to low levels of the gas during Sunday's leak and disputed reports that the chemical is as toxic as methyl isocyanate, the gas that leaked in Bhopal . The Institute plant also is the only U.S. producer of methyl isocyanate.

In addition to chemicals, Union Carbide makes Prestone antifreeze, Glad wraps and bags, Simoniz waxes and Eveready batteries.