Minnesota Mining and Manufacturing Co. reported yesterday that the quarter and half-year periods ended June 30 were the best in the company's 76-year history.

M13's second-quarter earnings rose 31.9 percent on a 15.9 percent gain in sales in the three months. Net income rose to $143.1 million ($1.23 a share) compared with $108.5 million (94 cents) a year ago.

Worldwide sales for the broad-based abrasives, chemicals and graphic systems company, best known to the consumer through its line of Scotch brand tape products, increased to $1.16 billion.

For the first six months of this year, net income totaled $262.4 million ($2.26 a share) an increase of 34.4 percent from $195.2 million ($1.69) in the same period last year. Sales for the first half advanced 15.9 percent to $2.24 billion.

Board Chairman Raymond H. Herzog said 3M's U.S. and international business contributed to volume gains and aided significantly in the growth of earnings.

PepsiCo Inc. reported that continued strength in the soft drink and snack food markets led to a 16 percent increase in profits for the second quarter compared with the same period last year.

Net income in the second quarter for the nation's second-largest soft drink maker was $57.3 million (65 cent a share) compared with $49.2 million (56 cents) for the same period in 1977, the company said.

Sales for the quarter were $989.7 million, up 19 percent from last year's $832.15 million, the company reported.

PepsiCo, which is headquartered in Purchase, N.Y. sells several types of soft drinks under the Pepsi-Cola brand name and other trade names and markets convenience and snack foods by Frito-Lay. Among its subsidiaries are Pizza Hut and Taco Bell restaurants, Wilson Sporting Goods Co., North American Van Lines Inc., and Rheingold Co., a brewer.

TRW Inc., a Cleveland electronics and space systems concern, reported an increase in its second quarter profits to $46.9 million ($1.48 a share) compared with $42.5 million ($1.33) in last year's second quarter. Sales rose to $956.3 million from $825.6 million.

TRW said the closing of a wire and cable plant would improve profits during the remainder of 1978 and would result in a "substantial" year to year prodfit improvement in 1979.

Six-month profit rose to $82.7 million ($2.58)from $566.8 million to $605.5 million.

First-half earnired with $1.6 billion.

National Steel Corp., the nation's third-largest steel producer, reported yesterday a 26 percent earnings improvement in the second quarter based on higher prices.

National said it earned $31.5 million ($1.64 a share) on sales of $924.8 million, compared with profits of $25 million ($1.30) on revenues of $852.2 million in the second quarter last year. Six-month earnings were $34 milliom ($1.77) a share) compared with $30 million ($1.56).

Stinson said a long strike at the Iron Ore Comapany of Canada, of which National is an 18 percent owner reduced earnings by as much as 30 cents a share.

Singer Co. reported yesterday that shrinking returns from itsmestic sewing-machine operations held the corporation's net earnings to a 2 percent gain in the second quarter.

"We now believe our U.S. sewing business will not be profitable this year," Singer Chairman Joseph B. Flavin said. "We believe that the market for sewing machines in the U.S. is declining at a more rapid rate than expected. As a result our volume for the year is now projected to be down from 1977."

In the second quarter, Singer earned $17.7 million (94 cents a share) compared with $17.4 million (92 cents) in the second quarter of 1977. Sales climbedfrom $566.8 million to $605.5 million.

FIirst-half earnings totaled $38.3 million ($2.06 a share) on sales of $1.2 billion. For the six month period last year, earnings were $36.2 million ($1.93) on sales of $1.1 billion.