| 摘要 |
PURPOSE:To obtain the titled binder for a magnetic recording medium having excellent characteristics by incorporating a linear thermoplastic polyurethane resin having respectively a not less than specified number of side chains of 1-4C aliphatic hydrocarbonic groups and of tertiary OH groups, and incorporating a low-molecular isocyanate having -NCO when needed. CONSTITUTION:For example, 1,4-butanediol and 1,3,5-hydroxy-3-methylpentane are added to adipic acid and polyester diol having CH3 at the side chain consisting of 2,2-dimethyl-1,3-propanediol and 1,4-butanediol, and the admixture is subsequently allowed to react with 4-4'-diphenylmethane diisocyanate. A thermoplastic polyurethane resin having in the molecular chain >=10, an average, 1-4C aliphatic hydrocarbonic groups and >=1 tertiary OH group as side chains is prepared in this way, and an isocyanate having >=2 NCO is incorporated into said resin to form a binder. A stable soln. which is readily soluble in solvents is prepared by using the binder, and a magnetic layer wherein magnetic powder is uniformly dispersed and which has high film strength and excellent adhesion to the supporting body and resistance to abrasion, etc. can be formed.
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