Feb 28 - Standard & Poor's Ratings Services today assigned its 'BBB+' senior unsecured debt rating to Pittsburgh, Pa.-based H.J. Heinz Co.'s $300 million of 1.50% notes due 2017 and $300 million of 2.85% notes due 2022. The notes will be issued under the company's Form S-3 shelf registration for debt securities. Heinz has indicated that net proceeds from this debt issuance will be used for general corporate purposes, including repayment of commercial paper. Heinz had about $5.0 billion o