A federal judge signed an order yesterday rejecting a request by Kennecott Corp. to void a New Jersey law the company said was blocking its attempt to take over Curtiss-Wright Corp.

And Curtiss-Wright directors unanimously rejected Kennecott's attempt to acquire the aerospace manufacturer for about $340 million in cash and stock as being "inadequate and not in the best interest of the company and its shareholders."

In addition to turning down Kennecott, U.S. District Judge H. Lee Sarokin also vacated a temporary order he issued Friday restraining Curtiss-Wright from invoking the New Jersey Corporation Takeover Law.

Kennecott, a metals producer, made a bid Friday to take over Curtiss-Wright of Wood-Ridge, N.J., by offering $40 a share in cash for up to 4.1 million shares for the remainder of hte Curtiss-Wright stock. Just two years ago, Curtiss-Wright tried to acquire the Stamford, Conn.-based Kennecott, and wound up with 14.3 percent of the stock of the leading copper producer and seats on its board of directors.

Kennecott won a temporary order the same day that blocked Curtiss-Wright from invoking a New Jersey statute restricting the takeover of corporations based in the state. Kennecott regarded the state law as more protective than federal rules.

Kennecott filed a motion before Sarokin yesterday asking that Friday's temporary order -- which blocked Curtiss-Wright from taking advantage of the New Jersey law -- be continued pending an appeal in the 3rd U.S. Circuit Court of Appeals.

Sarokin rejected the request and discontinued the temporary order.

In a related development, the New Jersey Bureau of Securities issued an order an hour later directing Kennecott not to make a takeover bid during the 20-day waiting period required by state law. Kennecott had proposed to begin its tender offer this Friday.

In other news of acquisitions and changes in management:

ConAgra Inc. has completed its acquisition of Banquet Foods Corp. for a purchase price estimated at $60 million.

A spokesman for ConAgra, an Omaha-based diversified food company, said Tuesday that a "few open issues" need to be resolved before details of the purchase for RCA Corp. are made public.

Banquet, based in St. Louis, makes fried chicken dinners, buffet suppers, boil-in-bag products, meat pies and desserts. It has annual sales of about $400 million and about 4,800 employes.

In an apparent attempt to foil furture takeover threats, Twentieth Century-Fox Films Corp. is studying the possibility of becoming a privately held company.

The giant film company announced Tuesday the stock transaction "would result in greater recognition of the underlying value that Fox believes is inherent in its assets than has been historically reflected in the market price of its common stock."

In raction to the announcement, the New York Stock Exchange suspended trading in Fox's stock. At the time, the stock was valued at $46.50 per share.

The plan under review calls for transferring an undisclosed amount of cash and assets to the company's stockholders in exchange for about 10.5 million outstanding shares currently worth a total of more than $480 million.

For the first time in the company's nearly century-long existence, there won't be a family member handling day-to-day affairs at the J. L. Hudson Co. department store chain.

Joseph L. Hudson Jr., 49, announced Tuesday that he will step down Jan. 5 as chief executive officer of the company founded nearly 100 years ago by his grand uncle.

Hudson, who will remain as chairman, will be replaced by P. Gerald Mills, 52, chairman and chief executive officer of the 16-store Dayton's department store chain based in Minneapolis. The Dayton Hudson Corp. took over Hudson's 11 years ago.

Mills also replaces Theodore A. Bintz Jr. as Hudson's president. Bintz assumes a new position of vice chairman.

Revco D. S. Inc., says it has purchased the 20-store May's retail drug chain from Lucky Stores, Inc., of Dublin, Calif.

The stores are located in Iowa, Illinois and Wisconsin.

Neither Revco nor Lucky Stores disclosed the amount of the cash transaction Tuesday.

Revco, a discount drug store chain, operates more than 1,300 stores in 26 states. Its sales exceeded $1 billion during the company's 1980 fiscal year.

A federal judge has granted the Securities and Exchange Commission a preliminary injunction against OKC Corp.'s chairman, Cloyce K. Box, and has demanded he present the court with a $5 million letter of credit.

District Judge Robert Hill also ordered the companS board of directors to appoint a "corporate committee" to oversee all transactions involving the sale, liquidation or transfer of the company's assets.

In its suit filed in mid-September, the SEC alleged that Box, chairman, president and shief executive officer of the Dallas-based company, received more than $5 million in kickbacks over the last seven years from various "friendly brokers."

The suit asks that Box be required to return the money to OKC and to resign from the company.

Cooper Industries, Inc., announced yesterday it has reached an agreement in principle to acquire Crouse-Hinds Co. of Syracuse for an exchange of stock.

Crouse-Hinds, an electrical products firm, has been involved for the last three months in a struggle to beat off a takeover bid by InterNorth of Omaha, holding firm for Northern Natural Gas Co.

Cooper, which is in energy, mining, aircraft services and consumer and industrial tools, has agreed to pay 0.725 share of Cooper common for each share of Crouse-Hinds common and 3.8918 share of Cooper common for each share of Crouse-Hinds preferred. Crouse-Hinds will make an exchange offer of common for 7.65 million shares of its preferred prior to the merger.