MIDDLEBURY, Conn. (AP) -- Chemtura Corp. said Thursday it will raise prices of compounds used in glass coatings, catalysts and synthesis applications because the specialty chemical maker's costs are rising.

 

Chemtura also is shortening the time it allows freighters it contracts to remain in port and raising the amount it charges vessels for remaining in port beyond set time periods. Known as ''demurrage,'' such contractual time limits and charges aim to cut idle time of vessels so those vessels can ship more cargo, thus increasing the revenue of companies that make and sell the cargo.

 

Beginning Tuesday, or as soon as contracts allow, the company will increase by as much as 20 percent its prices for butyl- and octyl-tin compounds. Such compounds are used in glass coatings and catalysts.

 

Costs for raw materials, including tin ingots, butene, aluminum and magnesium, are rising substantially, Chemtura said. Also, further cost increases are expected from ''the general escalation of labor costs and for logistic expenses resulting from high fuel prices and limited availability of cargo space on ocean going vessels.''

 

Also beginning Tuesday, the company will increase by as much as 40 percent its prices for aluminum alkyls, metal alkyl solutions and magnesium alkyls. Such substances are used in synthesis processes.

 

Costs for raw materials, including aluminum, magnesium, ethylene, solvents and ethyl-chloride, are rising or are expected to rise this year.

 

''Chemtura is investing in this core business to ensure continued security of supply on a global scale. Therefore, it is paramount that Chemtura achieves acceptable re-investment economics.''