Dispersant composition for magnetic media

Claim 2

A composition comprising the reaction product of: (a) from about 3 to 9 parts by weight of a phosphate ester represented by the formula ##STR16## wherein X is independently selected -from the group consisting of RO--, RO(R'O) n --and ##STR17## in which R represents an alkyl radical having from 2 to 18 carbon atoms, R' is an alkylene group having 2 to 4 carbon atoms, R" is an alkyl radical having 6 to 18 carbon atoms, n is an integer between 1 and 150 and the average value of m is between 1 and 2; and (b) from about 0.5 to 7 parts by weight of an alkali siliconate silylalkylphosphonate represented by the formula ##STR18## wherein A' is a hydrocarbon radical having from 1 to 18 carbon atoms, A is a divalent aliphatic hydrocarbon radical containing 1 to 4 carbon atoms or the benzylene radical, M is a cation selected from the group consisting of sodium, potassium, lithium, rubidium, ammonium and tetraorgano ammonium and k may have an average value of 0 to 3.

Claim 3

The composition of claim 1, wherein A is --(CH 2 CH 2 CH 2 )--, A' is methyl and M is selected from the group consisting of sodium, potassium and ammonium.

Claim 4

The composition of claim 2, wherein M is sodium.

Claim 5

The composition of claim 1, wherein said phosphate ester component is a blend of a mono-ester and a di-ester, X is selected from the group consisting of RO(CH 2 XH 2 O) n --and ##STR19## in which R and R" each have from 8 to 12 carbon atoms, n is between 5 and 40 and m is about 1.5.

Claim 6

The composition of claim 4, wherein A is --(CH 2 CH 2 CH 2 )--, A' is methyl and M is selected from the group consisting of sodium, potassium and ammonium.

Claim 7

The composition of claim 5, wherein X is ##STR20## and said phosphate ester blend is further characterized as having an acid number between about 60 and 120.

Claim 8

The composition of claim 6, wherein M is sodium, and k has an average value of about 0.1.

Claim 9

A magnetic coating composition comprising magnetic pigment particles, a binder for said particles and a dispersant for said particles, wherein said dispersant is the composition of claim 1.

Claim 10

A magnetic coating composition comprising magnetic pigment particles, a binder for said particles and a dispersant for said particles, wherein said dispersant is the composition of claim 5.

Claim 11

The magnetic coating composition of claim 9, wherein said binder is polyurethane and said magnetic pigment particles comprise iron oxide, cobalt-modified iron oxide or a metal alloy of iron, cobalt or nickel.

Claim 12

A magnetic coating composition comprising magnetic pigment particles, a binder for said particles, and a dispersant for said particles, wherein said dispersant is the composition of claim 2.

Claim 13

The magnetic coating composition of claim 11, wherein said binder is polyurethane and said magnetic pigment particles comprise iron oxide, cobalt-modified iron oxide or a metal alloy of iron, cobalt or nickel.

Claim 14

A process for producing a magnetic recording medium comprising: (i) mixing magnetic pigment particles, a binder for said particles, a dispersant and an inert organic solvent capable of dissolving said binder, to obtain a uniform dispersion thereof; (ii) coating said dispersion onto a non-magnetic substrate; (iii) orienting said magnetic pigment particles in a magnetic field; and (iv) removing said solvent from the coated substrate, said dispersant comprising the reaction product of (a) from about 3 to 9 parts by weight of a phosphate ester represented by the formula ##STR21## wherein X is independently selected from the group consisting of RO--, RO(R'O) n --and ##STR22## in which R represents an alkyl radical having from 2 to 18 carbon atoms, R' is an alkylene group having 2 to 4 carbon atoms, R" is an alkyl radical having 6 to 18 carbon atoms, n is an integer between 1 and 150 and the average value of m is between 1 and 2; and (b) from about 0.5 to 7 parts by weight of an alkali siliconate silylalkylphosphonate represented by the formula ##STR23## wherein A' is a hydrocarbon radical having from 1 to 18 carbon atoms, A is a divalent aliphatic hydrocarbon radical containing 1 to 4 carbon atoms or the benzylene radical, M is a cation selected from the group consisting of sodium, potassium, lithium, rubidium, ammonium and tetraorgano ammonium and k may have an average value of 0 to 3.

Claim 15

A process for producing a magnetic recording medium comprising: (i) mixing magnetic pigment particles, a binder for said particles, a dispersant and an inert organic solvent capable of dissolving said binder, to obtain a uniform dispersion thereof; (ii) coating said dispersion onto a non-magnetic substrate; (iii) orienting said magnetic pigment particles in a magnetic field; and (iv) removing said solvent from the coated substrate, said dispersant comprising the reaction product of (a) from about 3 to 9 parts by weight of a phosphate ester represented by the formula ##STR21## wherein X is independently selected from the group consisting of RO--, RO(R'O) n --and ##STR22## in which R represents an alkyl radical having from 2 to 18 carbon atoms, R' is an alkylene group having 2 to 4 carbon atoms, R" is an alkyl radical having 6 to 18 carbon atoms, n is an integer between 1 and 150 and the average value of m is between 1 and 2; and (b) from about 0.5 to 7 parts by weight of an alkali siliconate silylalkylphosphonate represented by the formula ##STR23## wherein A' is a hydrocarbon radical having from 1 to 18 carbon atoms, A is a divalent aliphatic hydrocarbon radical containing 1 to 4 carbon atoms or the benzylene radical, M is a cation selected from the group consisting of sodium, potassium, lithium, rubidium, ammonium and tetraorgano ammonium and k may have an average value of 0 to 3.

Claim 16

The process of claim 13, wherein A is --(CH 2 CH 2 CH 2 )--, A' is methyl and M is selected from the group consisting of sodium, potassium and ammonium.

Claim 17

The process of claim 13, wherein said phosphate ester component is a blend of a mono-ester and a di-ester, X is selected from the group consisting of RO(CH 2 CH 2 O) n --and ##STR24## in which R and R" each have from 8 to 12 carbon atoms, n is between 5 and 40 and m is about 1.5.

Claim 18

The process of claim 15, wherein A is --(CH 2 CH 2 CH 2 )--, A' is methyl and M is selected from the group consisting of sodium, potassium and ammonium.

Claim 19

The process of claim 16, wherein X is ##STR25## and said phosphate ester blend is further characterized as having an acid number between 60 and 120.

Claim 20

The process of claim 17, wherein M is sodium and k has an average value of about 0.1.

Claim 21

The process of claim 16, wherein said binder is polyurethane and said magnetic pigment particles comprise iron oxide, cobalt-modified iron oxide or a metal alloy of iron, cobalt or nickel.

Claim 22

The process of claim 14, wherein said binder is polyurethane and said magnetic pigment particles comprise iron oxide, cobalt-modified iron oxide or a metal alloy of iron, cobalt or nickel.