Abstract: An airflow drying device includes a granulated substance introduction portion, a dry process portion, and a product ejection portion. The granulated substance introduction portion includes a granulated substance inlet into which granulated substances are to be put, and a hot air inlet into which hot air is to be supplied. The dry process portion includes a loop pipe. The loop pipe is positioned laterally in a horizontal direction, and is able to dry granulated substances. The product ejection portion includes a cyclone collector where the granulated substances are collected after being dried through the loop pipe.

Abstract: A drying device 1 is an airflow continuous drying device, and includes a granulated substance introduction portion 11, a dry process portion 12, and a product ejection portion 13. The granulated substance introduction portion 11 is a stainless steel pipe 21, including a granulated substance inlet 22, into which granulated substances are put, and a hot air inlet 23, into which high-pressure hot air is supplied. The dry process unit 12 includes a loop pipe 25, which is made by winding a stainless steel pipe. The loop pipe 25 is arranged laterally in the horizontal direction, and is able to dry granulated substances in a highly efficient manner without turning the substances into powder. The product ejection portion 13 includes a cyclone collector 26, where the granulated substances are collected after being dried through the loop pipe 25.

Abstract: A magnetic recording medium comprising a lubricating layer comprising a fluorine-containing alkylsuccinic acid diester of the formula: ##STR1## wherein R.sub.1 is an aliphatic alkyl or alkenyl group, and one of R.sub.2 and R.sub.3 is a fluoroalkylether group and the other is a fluoroalkyl group, a fluoroalkenyl group, a fluorophenyl group, an aliphatic alkyl group or an aliphatic alkenyl group, which has excellent lubricity in an atmosphere having low to high humidity.

Abstract: A fluorine-containing alkylsuccinic acid diester of the formula: ##STR1## wherein R.sub.1 is an aliphatic alkyl or alkenyl group, and one of R.sub.2 and R.sub.3 is a fluoroalkylether group and the other is a fluoroalkyl group, a fluoroalkenyl group, a fluorophenyl group, an aliphatic alkyl group or-an aliphatic alkenyl group, which has excellent lubricity in an atmosphere having low to high humidity.

Abstract: Disclosed in this invention are novel fluorine-contianing compounds of a specific molecular structure having a fluoroalkylether terminal group, an aliphatic hydrocarbon terminal group and an imino terminal group in the same molecule and a molecular weight of from several hundred to about 3,000, and a process for preparing such compounds. The fluorine-containing compounds of this invention can be utilized as a lubricant composition for magnetic recording media.