British Ally Buys 9% Block of Ropak Stock : Investment: The company’s analysts see the sale as a vote of confidence in Ropak’s ability to win a patent-infringement suit filed by a competitor.

A British ally of Ropak Corp., a plastic-packaging manufacturer, has purchased a 9% block of its common stock for about $1.65 million.

The Linpac Group, based in Louth, Lincolnshire, on England’s eastern coast, bought the stock from two institutional investors, Massachusetts Mutual Life Insurance Co. and Mass Mutual Corporate Investors.

Ropak said the shares were priced at $4.50 each. In over-the-counter trading Tuesday, Ropak shares closed unchanged at $5.25.

Linpac and Ropak market each other’s materials-handling products. Linpac makes plastic, paper and metal packaging at 50 manufacturing sites in Europe and the United States.

Linpac acquired the block of 366,025 Ropak shares for investment purposes, according to Lippert/Heilshorn & Associates Inc., which handled the transaction.

William H. Roper, Ropak chairman and chief executive, and the company’s analysts see the sale as a vote of confidence in the company’s ability to win a patent-infringement suit filed in Detroit by a competitor, Perstorp Xytec Inc.

“Linpac has a good sense of the product and a good feel for the patent dispute, so I presume they have a comfort level about the dispute,” said Peter Melhado, chief investment officer for Horsburgh Carlson Investment Management, in New York. The company makes a market in Ropak shares, which means it is a guaranteed, regular trader of its stock.

Perstorp last year persuaded a federal judge to issue a preliminary order barring Ropak from making or selling several types of collapsible plastic bins used for shipping parts to factory assembly lines.

Ropak countersued in March, accusing Perstorp of libel and interfering in its relationship with customers. Ropak alleges that Perstorp had been telling Ropak’s customers that it is near bankruptcy.

The purchase will strengthen the marketing relationship between the two companies, said Mark Matheson, a research analyst for Cruttenden & Co., an Irvine-based mortgage banker.

“It keeps Linpac from breaking any agreement because it would hurt its ownership position,” Matheson said. “And, hopefully (for Ropak), they will sell more of your product.”

Last year, Ropak posted a $1.3-million loss on sales of $94 million, compared to a 1990 loss of $219,000 on sales of $93.2 million.