Fluorocarbon Co. in Laguna Niguel said it has agreed to sell its 50% ownership in Nitta-Moore, a plastics manufacturing operation in Osaka, Japan, to Nitta Industries for about $19 million in cash. The proceeds will be used to pay off loans. Fluorocarbon bought its interest in Nitta-Moore last May as part of a $70-million acquisition of Eaton Corp.'s polymer products group. Fluorocarbon borrowed about $60 million to make the purchase, which increased the company's total debt to $85 million. As part of the agreement, Fluorocarbon, which manufactures specialized plastic and rubber products and fluid-sealing devices, has extended a licensing agreement with Nitta-Moore through 1998.