A Utah state judge yesterday lifted a temporary restraining order and cleared the way for Curtiss-Wright to begin its proxy battle for control of Kennecott Copper Corp.

Kennecott meanwhile sent out a letter to its shareholders and ran full page newspaper ads questioning Curtiss-Wright's motives in waging the proxy fight.

Curtiss-Wright has purchased 9.9 percent of Kennecott's shares, has offered an alternative slate of 17 directors to run the company, and has indicated that if it gains control it will sell the Carborundum Corp. - which Kennecott purchased last year for 567 million dollars - and will distribute the proceeds to Kennecott shareholders.

Kennecott, in its letter, defended the purchase of Carbonundum, a highly profitable manufacturer of abrasives, and said that it board today "is even more strongly of the opinion that Carborundum is a sound acquistion."

The company noted that Curtiss-Wright did not begin to purchase its shares of Kennecott until after the acquisition of Carborundum was completed.

"If Curtiss-Wright objected to that acquisition why did it then buy Kennecott stock?" the letter asked.

Utah Judge David K. Winder vacated his restraining order and refused to issue the preliminary injunction which was requested by the Utah Commissioner of Business, who claimed Curtis-Wright had violated the state's takeover statute. A large part of Kennecott's assets are in Utah.

Winder ruled the Utah-courts had no jurisdiction over Curtiss-Wright's acquisition of the Kennecott shares. Attorneys for the state said they expected to appeal the ruling to the Utah Supreme Court. A spokesman for Kennecott indicated the company may also appeal.

Curtiss-Wright, which was waiting for the Securities and Exchange Commission to clear its proxy materials so it can proceed with its fight, said it was constrained from commenting.