Armour & Co. yesterday signed a pattern-setting agreement for the nation's meatpacking industry with the United Food and Commercial Workers International Union that essentially freezes all wage and cost-of-living increases through August 1985.

Union officials said they hope that the contract will serve as a pattern for the industry, which had been demanding a rollback of union benefits. "It's a pattern. It's something we've been working on for two years," said Jay Foreman, a union vice president.

In exchange for the wage freezes, Armour agreed not to close any of its plants for the next 18 months and to give notice of any plant closings for the next 12 months. The company also has given the union a five-year estimate of its capital expenditures for its plants and will provide the union each January with a summary of capital expenditures at each individual plant for the preceding year.

Foreman said that in addition to Armour, Wilson Food Corp. signed a similar agreement earlier this week, and the employes at Hormel are voting on a contract. He said management officials at John Morrell & Co. and Swift are considering similar contract proposals from the union.

The agreements amount to the first major settlements of the 1982 round of contract bargaining. The union's national contract agreement with the industry was not scheduled to expire until Aug. 31.

Next year is the start of a new three-year round of bargaining, with contracts in the major industries expected to set a pattern for subsequent years. In addition to the meatpacking industry, the Teamsters union appears on the verge of settling a new national freight agreement with the trucking industry in which almost all wage increases will be in the form of future cost-of-living protection. The current contract expires next March 31.

Under terms of the Armour agreement, cost-of-living increases due in January and July 1982 will be suspended and there will be no cost-of-living protection for the remainder of the agreement. The new contract does provide for an unspecified lump-sum payment to "eligible" employes in December 1983.

The contract also places a moratorium on all wage increases until August 1984. The contract can be reopened to negotiate wages at that time if the union wants.

In addition to the basic freeze in wage and cost-of-living increases, the new contract provides lower wage rates for new employes at Armour plants.

Armour Chairman John W. Teets called the new agreement a "historic first," describing it as "an instance of statesmanship on the part of the union."

Foreman said the contract represented "substantial concessions" on the part of the union but emphasized that the goal was to protect the increases already won by the membership rather than allow a rollback.