Coating of fine particles in polyurethane block copolymer binder
AssigneeMinnesota Mining and Manufacturing Company
InventorsRussell L. Vermillion, William A. Bernett
Life of this patent
Estimating the term…
Abstract
Coating of fine particles such as magnetizable particles in a binder which is a soluble hydroxyl-terminated polyurethane block copolymer comprising soft or flexible blocks synthesized from polyester or polyether diols and hard blocks synthesized from aliphatic diols containing tertiary amine and p,p'-diphenylmethane diisocyanate. The block copolymer is capable of dispersing as well as acting as a binder for the particles.
Claims14
In a coating comprising fine particles and a binder on a substrate, the improvement comprising:
- said binder primarily comprises a hydroxyl-terminated polyurethane block copolymer comprising
- polyester or polyether segments, each having an average molecular weight of 200-3000,
- short-chain aliphatic segments, 10-100 mole percent of which contain tertiary and/or quaternary nitrogen, and
- symmetrical, unbranched, aromatic urethane segments interconnecting the polyester or polyether and short-chain aliphatic segments the terminal hydroxyls being connected to said short-chain aliphatic segments.
In a magnetic recording medium comprising a backing member and at least one coating comprising fine particles and a binder, the improvement comprising:
- said binder comprises a hydroxyl-terminated polyurethane block copolymer comprising
- polyester or polyether segments each having an average molecular weight of 200-3000,
- short-chain aliphatic segments, 10-60 mole percent of which contain tertiary and/or quaternary nitrogen, and
- p,p'-diphenylmethane urethane segments interconnecting the polyester or polyether and short-chain aliphatic segments.
Process for applying to a substrate a coating of fine particles and binder comprising the steps of
- (a) inter-reacting in solution excess soluble symmetrical, unbranched, aromatic diisocyanate with hydroxyl-terminated polyester or polyether having an average molecular weight of 200-3000 to provide a mixture of isocyanate-capped polyurethane and unreacted aromatic diisocyanate,
- (b) chain-extending the mixture with short-chain aliphatic diol, 10-100 mole percent of which contains tertiary nitrogen to produce a soluble hydroxylterminated polyurethane block copolymer,
- (c) mixing said polyurethane block copolymer with fine particles and sufficient volatile vehicle to provide a coatable dispersion wherein the weight of the particles exceeds that of the copolymer,
- (d) coating said dispersion onto a substrate, and
- (e) drying the coating.
In the manufacture of a magnetic recording medium comprising a backing member and at least one coating comprising fine particles and a binder, a process for applying said coating comprising the steps of:
- (a) inter-reacting in solution excess soluble symmetrical, unbranched, aromatic diisocyanate with hydroxyl-terminated polyester or polyether having an average molecular weight of 200-3000 to provide a mixture of isocyanate-capped polyurethane and unreacted aromatic diisocyanate,
- (b) chain-extending the mixture with a short-chain aliphatic diol containing tertiary nitrogen,
- (c) further chain-extending with a short-chain aliphatic diol which has no tertiary nitrogen in an amount providing 40-90 mole percent of the total diol to produce a soluble hydroxyl-terminated polyurethane block copolymer,
- (d) mixing said polyurethane block copolymer with fine particles and sufficient volatile vehicle to provide a coatable dispersion wherein the weight of the particles exceeds that of the copolymer,
- (e) coating said dispersion onto a substrate, and
- (f) drying the coating.
Dependencies are inferred from the claim text.