MEXICO CITY, May 31 (Reuters) - Mexican petrochemical company Alpek said on Tuesday it has finalized its $620 million acquisition of PET laminate producer Octal Holding.

The deal is expected to generate an additional $120 million in revenue for Alpek through the end of the year as demand for polyester grows, the company said in a filing to the primary Mexican stock exchange.

Alpek, a subsidiary of conglomerate Alfa, signed the agreement in February and said in a call with investors last month it expected the deal to be completed by the end of the second quarter.

"We are pleased to have completed this acquisition ahead of schedule," Chief Executive Jose de Jesus Valdez said in a statement.

Analysts at Mexico's Monex called the announcement "positive" for Alpek in a note Tuesday, saying the acquisition will allow it to diversify its portfolio and increase cash flow in the medium and long term. (Reporting by Kylie Madry; editing by Richard Pullin)